Another vote for The Name of the Wind (672 pp), and ditto being very impatient about the sequel not coming out yet!
The Lies of Locke Lamora (752 pp) and its sequel Red Seas Under Red Skies (784 pp) go very fast. Another case of series-interruptus, though.
You can get several Lois McMaster Bujold titles as omnibuses. Cordelia’s Honor (608 pp) is a good one to start with. Bujold is one of my very favorites, especially in hero/military sci fi mode (e.g., Miles Vorkosigan stuff, which *Cordelia’s Honor *begins). Her two more recent fantasy series are also good.
Robin Hobb is a notorious brick-maker. The covers of her paperbacks are much more garish and mass-markety than I think they should be; I think she’s a pretty nuanced, subtle, unexpected writer. I’ve deeply enjoyed the Farseer trilogy (464/675/757 pp), the Tawny Man trilogy (688/736/928 pp), the Liveship Traders trilogy (832/864/816 pp), and the Soldier Son trilogy (624/752/704 pp) (though I understand many of her fans didn’t like that last one so well).
Connie Willis’ Passage has 780 pp in paperback. The rest of her stuff is not so long, but deliriously good, especially The Doomsday Book (592 pp) and To Say Nothing of the Dog (512 pp). Great history mixed with science fiction.
Another vote for Guy Gavriel Kay: the omnibus of the Fionavar Tapestry is 792 pp. Tigana is 688 pp. Note that this author frequently writes fantasy with very thinly disguised but well-researched European history in it; most of it takes place in some other world with two moons, but there are nonetheless recognizable medieval French, Moorish Spaniards, Vikings, etc. in various volumes. The Fionavar Tapestry starts on Real Actual Earth before moving to an alternate reality, but his others are all in-universe. He notes in several acknowledgments that he’s writing historical fiction in a fantasy wrapper, though.
Acacia (753 pp) by David Anthony Durham, who usually writes straight-up historical fiction, is a great fantasy work. Its sequel is due in September!
I adored Anathem (will be 1008 pp in paperback, but only available as hardback for now) by Neil Stephenson, but like his Baroque Cycle, it takes some work. A less glossary-intensive one of his, originally under a pen name with his uncle, is Interface (641 pp). That’s politics and intrigue with just a dash of near-future sci fi.
You can get C.J. Cherryth’s Faded Sun trilogy as an omnibus (784 pp). She’s got other omnibuses too, though I haven’t read them yet. I liked the Faded Sun. Wikipedia describes it as “military science fiction” but I think I’d call it more political/cultural or world-building than military.
Ditto the posters above on finding too much formulaic-ness in Diana Gabaldon. I really wanted to like her books, but didn’t.