Tor's one-volume omnibus edition of The Wheel of Time proved surprisingly unpopular with booksellers.
The Lord of the Rings was, for its day, unusual in its length. At 470,000 words it massively outsized The Hobbit at 97,000 words, and The Hobbit was considered long for a children's novel. However, that length allowed Tolkien to explore his fictional world in some depth, treating it like a place that had actually existed, and putting a lot of detail into the people and places. Whilst writing such long books is time-consuming and publishing them problematic, Tolkien's achievement meant that length came to be a feature of the epic fantasy subgenre.
Indeed, many later series are so huge that individual volumes are almost as long as The Lord of the Rings in its entirety. To Green Angel Tower, the concluding book of Memory, Sorrow and Thorn by Tad Williams, is over 520,000 words in length, making it the longest epic fantasy novel ever written and one of the longest-ever books written in English. Two volumes of A Song of Ice and Fire - A Storm of Swords and A Dance with Dragons - exceed 420,000 words in length. Two recent epic fantasy novels, The Wise Man's Fear by Patrick Rothfuss and Words of Radiance by Brandon Sanderson, just go over 400,000 words. The Wheel of Time, in its entirety as one story, is over 4,360,000 words. This shows that while writing long novels may give publishers a headache, it can pay off.
However, some authors have reacted against such huge lengths. Joe Abercrombie's First Law novels crept over 200,000 words with Last Argument of Kings and he pulled back the length with Red Country. His recent Shattered Sea novels are considerably shorter, resulting in a more focused narrative and also faster turn-around times. Terry Pratchett, disdainful of both unnecessary doorstops and cliffhangers, didn't even get above 100,000 words until he was twenty-three books into his Discworld series. Paul Kearney, the author of The Monarchies of God, The Sea-Beggars and The Macht Trilogy (and some very fine stand-alones), writes very slim volumes which have occasionally been cited as a reason for his relative obscurity, with some fantasy readers preferring big doorstops and passing over short novels on the bookshelves.
Ironically, given that by modern fantasy standards it's quite short, the precedent of The Lord of the Rings gave authors the freedom to write long stories with the confidence that readers would stay with them. This has been both a good and bad thing for the genre.
Sometimes less is more when it comes to creation myths.
J.R.R. Tolkien began consciously creating Middle-earth in 1917 (and subconsciously several years earlier). By the time The Hobbit was published, he'd already been working on it for over twenty years. By the time The Return of the King was released, Middle-earth had existed in Tolkien's head and on numerous pieces of paper for just shy of forty years. In that time Tolkien had expertly crafted the history, geography and languages of his fictional world, giving him an immense reservoir of material to draw on.
This also gave readers and budding fantasy authors an appetite for "worldbuilding", expertly crafting a world so convincing in its solidarity and background that the reader would be fully immersed in the experience.
Of course, most fantasy authors don't have twenty years to prep their world ahead of writing the book, so they tend to do both the novel-writing and the worldbuilding at the same time. This is actually in keeping with what Tolkien did. Although Tolkien had created Middle-earth twenty years before starting The Lord of the Rings, all of that action and focus had been in Beleriand, the lands west of the Blue Mountains destroyed at the end of The Silmarillion, or on the western continent of Aman. For The Lord of the Rings itself Tolkien had to create Third Age Middle-earth as he went along. Gondor, Rohan and Mordor did not exist in his mind before he started writing the book, and indeed he took lengthy breaks from the writing to fill in their histories, develop their cultures and draw maps (see below).
Years later George R.R. Martin would allude to this. When he started writing A Game of Thrones, he had no idea who any of these people were or what they were doing. He didn't draw a map until he was a hundred pages into the writing, and never created a language for the books: when he needed a Dothraki word, he'd create it and try to remember it in case it cropped up again. He made it up as he went along, with the history of Westeros accumulating in stages. It was only later, and after some errors and inconsistencies were pointed out by fans, that Martin sat down and did worldbuilding in serious detail, but again nowhere near that practised by Tolkien (at least, not until he knew it was going to be published in The World of Ice and Fire and the planned Fire and Blood volume). In Martin's parlance, Tolkien created a vast iceberg of detail, with only a small amount showing above the surface in the novels but much more remaining out of sight. Martin and many other modern fantasy authors prefer to create the illusion of the iceberg, without the time-consuming job of actually creating things that would never be seen but giving a sense that they are still there.
An exception to this would be Ed Greenwood. In 1967 (at the age of eight!) Greenwood began creating a fantasy world in which he would set various short stories. This was soon replaced by creation for creation's sake, with a purpose given to it when he began setting Dungeons and Dragons roleplaying games there a decade later. In 1987 TSR, the publishers of D&D, were so impressed that they bought the setting for commercial release. Today the Forgotten Realms stands the most detailed, exhaustively-researched fantasy world ever created, and one where the published materials in the Realms (now spanning 300 or so novels, more than two dozen computer games, 100+ gaming materials and a forthcoming feature film) are apparently still outmatched by Greenwood's private notes.
Tolkien made worldbuilding a cornerstone of fantasy, but also warned of getting carried away with it and neglecting the story and characters in favour of "subcreation".
Diana Wynne Jones's map of Fantasyland for The Tough Guide to Fantasyland. As you can tell, an enormous amount of thought and originality went into this map, carefully constructed to reflect that of a lot of contemporary epic fantasy novels.
Maps in fantasy novels did not begin with Tolkien. Jonathan Swift's 1726 classic Gulliver's Travels has maps of the various islands Gulliver travels to, whilst The Wonderful Wizard of Oz, The Worm Ouroborus and Robert E. Howard's Conan stories all had maps accompanying the text, as did C.S. Lewis's Narnia books. Tolkien did perhaps go a bit further than most, though. The Lord of the Rings has a big frontispiece map showing the whole of western Middle-earth. There is also an additional map of the Shire, and then, accompanying The Return of the King, a more detailed map of Rohan, Gondor and Mordor. And although he did not publish them in his lifetime, Tolkien also drew illustrations and maps of locations in the books, such as Isengard and Minas Tirith.
For a while after Tolkien, maps ruled the fantasy roost. The Sword of Shannara by Terry Brooks, set in the Four Lands, features a map of the entire landmass. The two sequels, set in the Westland and Eastland respectively, feature more detailed maps of those locations. Lord Foul's Bane by Stephen Donaldson is intended (at least partially) as a literary deconstruction of fantasy, but Donaldson knew he still needed to have a map of the Land at the front of the book. Raymond E. Feist had two maps, one of each of the two planets his novel Magician takes place on. David Eddings, who was cheerfully and openly inspired to write The Belgariad because of the success of The Lord of the Rings, doubled down on maps. His fantasy series would visit a new kingdom or region almost every other chapter, and zoomed-in maps would appear when required (or even when not required). Tad Williams did the same in Memory, Sorrow and Thorn, sometimes showing maps of regions completely different to where the action in that section was taking place.
The presence of the map was soon apparently mandatory in fantasy novels, leading some to rebel against it. David Gemmell refused to include a map of the Drenai Empire in Legend, feeling it would limit creativity. Many years later, tiring of reader requests for a map, he selected the fan map he liked best and used that. Richard Morgan did the same with his Land Fit For Heroes series, not including a map in the first book and challenging fans to produce one for later volumes. Glen Cook did not include a map in his Black Company novels, although he later allowed a roleplaying company to create one (grudgingly, it appears, approved by himself) for a rulebook. Terry Pratchett was absolutely dead-set against maps appearing of the Discworld, believing that maps inhibited creativity. Stephen Briggs changed his mind by producing a coherent, detailed map of Ankh-Morpork. Pratchett found just studying the map gave him ideas for future stories and, reluctantly, allowed an official map of the Discworld to appear in The Discworld Mappe, published in 1995 some twelve years after the first novel in the series was published.
Some authors seemed to enjoy even mildly trolling readers over the matter. Steven Erikson and Ian Esslemont's Malazan novels features many splendid maps, but sometimes and inexplicably of completely different continents to where the action in the novel actually takes place. Large swathes of action falls outside the boundaries of any map. Ian Esslemont, notably, has lots of events happening in Stratem, the home of the Crimson Guard, but has never released a map of the continent. Details and directions in the books themselves can also be highly contradictory (the eventually-confirmed location of the Lether continent, for example, seemed to directly contradict statements in earlier novels). Joe Abercrombie also refused to provide a map of the Circle Sea region in his First Law trilogy, but later relented and released maps of the locations in Best Served Cold, The Heroes and Red Country. Amusingly, he still declined to release maps for the earlier books, but did sneak a map of the entire known world into a single frame of the comic book adaption.
At other times, authors liked to hedge their bets. George R.R. Martin provided maps for Westeros in A Game of Thrones, but decided against releasing a map of the eastern continent, aside from a small portion in A Storm of Swords. It took twelve years for the eastern continent to even get a name (Essos) and a further four beyond that for HBO to release the first map of the known world. And even then Martin wasn't happy with it, almost completely redrawing and reconceptualising it for The Lands of Ice and Fire.
So, maps. Some readers will put a book down if they don't have a map in them, some won't touch them with a bargepole if they are present. But we have Tolkien to thank for their seeming omnipresence in the genre.
Tolkien's motives in writing The Silmarillion and The Lord of the Rings stem, in part, from his love of language and of creating new languages. During his lifetime Tolkien developed two languages in detail, these being Quenya and Sindarin. He also sketched out several other languages in a less-developed form, including Dwarfish and the Black Speech of Mordor. Needless to say, this took quite a long time.
Modern fantasy authors, generally speaking, don't have time or knowledge or background to sit down and create entire languages from scratch. As mentioned above, most authors simply invent a word or two and try to remember them for later on if needed again.
Some exceptions exist. M.A.R. Barker created the language of Tsolyáni in the 1940s, which eventually saw publication in the Empire of the Petal Throne roleplaying game in 1975. Marc Okrand also created a working Klingon language for the Star Trek films in the 1980s. However, it wasn't until The Wheel of Time in 1990 that a major work of epic fantasy employed a functioning fictional language. Robert Jordan developed a vocabulary of over 1,000 words for the Old Tongue used in the novels and rules to go along with it. Only a small amount of this material ever made it into the novels, but a more comprehensive account of the language is planned for The Wheel of Time Encyclopedia.
In more recent times, it has become more fashionable to create entire languages for works of fiction. James Cameron commissioned linguist Paul Frommer to create a language for the Na'vi in his 2009 film Avatar. When HBO created the Game of Thrones TV series, based on George R.R. Martin's novels, they hired linguist David Peterson to create a working Dothraki language for the show. Later on he expanded this with Valyrian and elements of other languages. Peterson also went on to create more fictional languages for Thor: The Dark World, Defiance and The 100.
Still, it is relatively unknown for epic fantasy writers to create entire languages for their novels, this being an area that Tolkien was uniquely suited to deal with.
Tolkien also popularised the use of the "traditional" fantasy races: elves, dwarves, orcs, goblins, monstrous wolves and so on. Whilst the use of these races did not originate with Tolkien, he did shape them into their most familiar form, where the elves are long-lived, semi-immortal and graceful, the dwarves are miners fond of drinking and battle, and orcs are marauding, malevolent raiders. Tolkien drew on mythology for his sources, although he did change things around: elves in fairy tales and myths tended to be more mischievous or even capriciously evil races (in which form Pratchett deploys them in his Discworld novels Lords and Ladies and The Shepherd's Crown).
Amusingly, Tolkien originally considered using the word "gnome" for his long-lived, immortal species, drawing on its association with wisdom and knowledge ("gnomic", "gnosis"). However, in the 1920s and 1930s there was a boom in the popularity of garden gnomes (a fad imported from Germany) and Tolkien seems to have decided that the word was no longer appropriate. Gnomes would go on to appear in Dungeons and Dragons, but the only epic fantasy writer of note who would make major use of them would be Terry Brooks, who employed them as an antagonistic race in The Sword of Shannara.
Many fantasy writers would go on to use the races in their Tolkien-esque mode, although sometimes not using the same name. Elves and dwarves would show up pretty much as described in Tolkien in Raymond E. Feist's work, although later Riftwar books would stop using them (to the point where readers began to wonder if Feist had forgotten there were even dwarves on Midkemia). David Eddings, despite his publicly-state desire to make money from cashing in on the Tolkien crazy, actually eschewed using any of the familiar races. Tad Williams used them in Memory, Sorrow and Thorn but changed the names: the elves became the Sithi (a common alternate name for the elves, borrowing from the Irish Sidhe) and the dwarves and hobbits became mixed together a little to form the Qanuc (confusingly described as "trolls" in the novels). Dennis L. McKiernan's Iron Tower trilogy employs both elves and dwarves in the standard mode.
More recent epic fantasy either dispenses with the elves and dwarves together (such as Wheel of Time and A Song of Ice and Fire, although the latter's Children of the Forest do have some elf-like qualities) or changes them much more substantially. Steven Erikson's Malazan Book of the Fallen features the Tiste, an elf-like immortal species famed for their skills in battle and with sorcery who have become divided into several, occasionally warring factions. Scott Bakker's Second Apocalypse mega-series features the very elf-like Nonmen, who have been driven insane by their longevity and the horrors they have witnessed over the course of thousands of years.
What is slightly more unusual is the lack of appearance of hobbits in later fantasy work. The word "hobbit" itself is copyrighted (unlike the very generic terms "elf" and "dwarf"), but Tolkien drew on pre-existing ideas in the creation of the race. Dungeons and Dragons would in fact develop two successors to hobbits, in the form of halflings (a word Tolkien himself deploys in The Two Towers) and, in the Dragonlance world, the fearless kender. McKiernan's Iron Tower series, itself originating from a failed attempt to write an authorised sequel to The Lord of the Rings, features the diminutive Dwarrows. However, most subsequent fantasy authors have preferred to use actual humans (usually callow youths from a rural background) in place of hobbits: Rand, Mat and Perrin in The Wheel of Time, Simon in Memory, Sorrow and Thorn, the Ohmsfords of Shannara and Garion of The Belgariad can all be seen as the successors of the hobbits, despite being human.
In The Lord of the Rings Tolkien employs a number of themes he develops through the work. He is concerned with the corruption of power, personified in Sauron and Saruman, and the effect that the One Ring has on characters such as Boromir. He also explores the idea of redemption, with Gollum, almost destroyed by the Ring, very nearly redeemed by Frodo before he finally falls under the spell of the Ring one last time. However, Bilbo's act of mercy in The Hobbit (by not killing Gollum when he had the chance) is revealed to have been crucial in ensuring the ultimate victory over Sauron.
There's also a tremendous sense of nostalgia for a bucolic past replaced by a technological future. Tolkien is often mischaracterised as a Luddite, when in fact he saw the practical value of progress, such as when in old age he learned to drive and bought himself a car for the freedom it gave him and his wife, despite his dislike of the environmental damage wrought. However, Tolkien did strongly believe in the dehumanising effect that technology brought to warfare, seeing for himself the impact of industrial slaughter on the Western Front of World War I. He was later repulsed by the idea of mass aerial bombardments of civilian targets and the deployment of nuclear weapons. This disdain for technological warfare shows up in The Lord of the Rings through elements such as the Scouring of the Shire and Saruman tearing down the woods and groves of Isengard to create weapons factories.
Tolkien also wrote The Lord of the Rings as a bittersweet tragedy. Yes, Sauron is defeated but the world is forever changed. The elves and dwaves have no place in the world any more and Frodo is so traumatised by his experiences he must leave his home forever and seek succour in the west. Tolkien believed that change was a fundamental part of human life and you could never step back, a core theme of his work that is curiously often misunderstood or ignored (most notably in Michael Moorcock's well-written but poorly-supported "Epic Pooh" essay).
Later works of fantasy would, for the most part, abandon any kind of substantial thematic development in favour of being purely entertaining: there's not too much literary depth to be found in the Shannara or Belgariad books, which exist really as popcorn novels (not that there's anything wrong with that). However, some of the stronger and better works of epic fantasy do engage with ideas and themes beyond being entertaining, and emerge the better for it. The Black Company studies the morality of evil in a way few works (fantasy or not) manage. Memory, Sorrow and Thorn ponders the idea of inherent racism in works of fantasy. Legend and much of David Gemmell's work asks what exactly heroism actually is. The Wheel of Time concerns itself with gender issues, sexual equality and how the "chosen one" may fall to evil due to the stresses placed upon him or her. A Song of Ice and Fire is primarily concerned with power, who wants it, who disdains it, who takes it up reluctantly and who hungers for it. The Malazan series engages with a whole host of themes, running from capitalism to mercy, and, for all of its myriad faults, at least The Sword of Truth aspires to socio-political ideas (if often in a morally questionable form). However, the greatest explorer of themes in fantasy was Terry Pratchett, who used his Discworld books to examine everything from religious fanaticism to the development of steam technology to the power of propaganda.
So the influences Tolkien brought to epic fantasy were many and varied. The impact of The Lord of the Rings was so immense that it took a surprising amount of time for other writers to begin exploring some of his ideas and bring their own to the table.