Excluding textbooks that I have no way of finding out how many pages they were, I read The Whirlwind of War: Voices of the Storm, 1861-1865 by Stephen B. Oates which has 718 pages of text.
Possibly War and Peace. The paperback was a little over 1100 pages. But I would suspect that DFW's Infinite Jest is longer in terms of word count, esp. taking into account the footnotes, which are part of the story. That was pretty close to 1100, IIRC. Edit: oops. Amazon says it was Robert Burton's Anatomy of Melancholy, at 1424 pages. Multi-volume books it's hands down LaGrange's biography of Gustav Mahler. The 4th and final volume is subtitled "A Life Cut Short" and (edit!) Amazon tells me that, at 1758 pages, it is also the winner for the longest single volume. The other volumes were pretty close to 1000 pages.
Something like The Lord of the Rings - JRR Tolkein 1,216 pgs Battlefield Earth - L Ron Hubbard 1,050 pgs (yes, that one, but long before it ever graced screens) The Brothers Karamazov - Fyodor Dostoyevsky ~1,000 pgs Coincidentally I happen to have it on my desk atm* and it's 1,079 pages to be exact (soft cover). I have it thinking that someday I will finish it (<3 David Foster Wallace, RIP), but I have only read the first maybe 150 pages a long time ago and barely had any idea what was going on. (* The reason I have it out is the book is actually so thick that I'm using it to prop something up with an irreparably broken base and it's the perfect size. )
Well, Les Miserables is sitting here at 1264 pages while The Stand checks in at 1153 pages. The Rise and Fall of the Third Reich is also 1264 pages, which really can't be a coincidence.
That's an interesting point. Some of the badly-written literary theory I had to read in grad school seemed interminable. I'll have to see if I can remember what books I had to read standing up in order to not nod off... Probably Frederic Jameson's Signature of the Visible
Best use for it........... I'm thinking that maybe Stephen Donaldson's Chronicles of Thomas Covenant clocks in at around 3,000 pages.
I was actually mis-remembering and didn't get around to looking up the page count for the signet paperback. I don't have it anymore.
Currently reading History of the United States of America During the Administrations of Thomas Jefferson ( Henry Adams), which is 1252 pages, unless it counts as 2 books. Next up is The Way We Live Now (Anthony Trollope), 952 pages. The Brother Karamazov may be longer, but I read it years ago and don't have the book anymore to check the page count.
My War and Peace stands at 1215, that's the Pevear/Volokhonsky translation. I just started In Search of Lost Time which should trump all in terms of length - wish my luck...
Most of my physical book collection is elsewhere now, so I don't have definite page counts, but if I had to guess I would say: Les Miserables (unabridged) Brothers Karamazov I'm not counting Lord of the Rings as it's in 3 volumes.
Atlas Shrugged - But I really enjoyed it so it didn't seem to take forever. But the 90 page speech by John Galt was difficult to get through.
I read the whole of The Life and Times of Pancho Villa (footnotes and bibliography and all), which checked in at 1004 pages. And I didn't think it went on too long - most sections were relatively succinct.