Tad Williams has broken his own record to deliver the longest epic fantasy novel of all time, at least before the editing process is completed.
Williams' 1993 novel To Green Angel Tower, the concluding volume of Memory, Sorrow and Thorn, is 520,000 words in length, or around 60,000 words longer than even the complete Lord of the Rings. In fact, the only even vaguely SFF novels longer than To Green Angel Tower are firmly in other subgenres: Varney the Vampire, Atlas Shrugged, Jerusalem and Infinite Jest. To Green Angel Tower is as long as the first two books in the trilogy (The Dragonbone Chair and Stone of Farewell) combined and is often only available in two volumes.
Fittingly, Williams' new, record-breaking novel is the concluding volume to Memory, Sorrow and Thorn's sequel trilogy, The Last King of Osten Ard. The Navigator's Children currently clocks in at "bigger" than To Green Angel Tower.
The novel is being "prodigiously cut" and may end up coming in shorter than the published To Green Angel Tower, but whether that happens or not remains to be seen.
The Navigator's Children is currently tentatively scheduled for release in late 2021, and will be preceded by a short novel called Brothers of the Wind (previously known as The Shadow of Things to Come), which focuses on the backstory of the Storm King, Ineluki, and his brother Hakatri.
CORRECTION: It's been noted that Tad has completed the first draft of The Navigator's Children and is now revising, but has not delivered it to DAW as yet.