Black Library and Games Workshop have announced the actual, final novel in The Horus Heresy, their absolutely massive prequel series to their Warhammer 40,000 science fantasy setting. The series began in 2006 with Dan Abnett's Horus Rising, so it is only fitting that Abnett is bringing the saga to an end with The End and the Death. However, the story proved too titanic to fit into one volume, so will be published in (at least!) two books.
The Horus Heresy is the story that provides the mythic underpinning to the Warhammer 40,000 universe. Set ten thousand years before the "present" in the setting, the saga tells of the rebellion of the Warmaster Horus against his father, the immortal Emperor of Mankind. Horus believes his father has become a despot and a tyrant, wanting to be worshipped as a god. However, Horus has also been manipulated by the insidious forces of Chaos. Almost half the forces of the Imperium of Man join Horus in his rebellion, designed to overthrow the Emperor and "free" humanity. However, many legions remain loyal to the Emperor, leading to a desperate, seven-year war that will determine the fate of humanity and the galaxy.
The End and the Death is also the final book in the Siege of Terra sub-series. This eight (now nine+) volume series depicts Horus's final gambit, a breach of the defences around the Solar system and a full-scale assault on Holy Terra with almost his entire remaining army and fleet, relying on a Warp Storm to prevent reinforcements from reaching Sol before he can overthrow the Emperor. The previous seven books in the sub-series - The Solar War, The Lost and the Damned, The First Wall, Saturnine, Mortis, Warhawk and Echoes of Eternity - depicted the monstrous fight raging for the throne world, not to mention the culmination of many subplots as various enemies face off for the last time. The End and the Death sees the depiction of the most iconic event in Warhammer 40,000's lore, when the Emperor directly intervenes in the war and faces his son Horus for the final time. But that is only part of the story.
Abnett is the Black Library's most acclaimed and biggest-selling author (not to mention Britain's third-biggest selling science fiction author, behind only Peter F. Hamilton and Alastair Reynolds) and recently delivered a stunning two-part finale in his Gaunt's Ghosts series, with the brilliant duology of Warmaster and Anarch (not the final books in the Ghosts series, but the final for a while). Delivering the end of the series is a huge order, but Abnett will hopefully rise to it.
The stats for The Horus Heresy are mind-boggling. The series will now comprise 63 books in the core series (55 novels and 8 short story collections), 48 audio dramas, 2 art books, 2 script books and 1 graphic novel. The combined page count of the main series (not counting the last two) is 26,881 pages in paperback, or two Wheel of Times with an entire Song of Ice and Fire to follow up (though Horus Heresy books have fairly large print, so I suspect the word count is not quite so insane, with some estimates placing it around 7 million, which is about 1.6 Wheel of Times).
The End and the Death: Volume 1 is due for publication in 2023.