Mitchener's Aztec

Actually, that was by Gary Jennings. I got about halfway through it before giving up in disgust.

As for other long books I've read... Les Miserables (the unabridged version, naturally), several of Michener's (my favorite Michener is The Source), Shogun by James Clavell, Diana Gabaldon's time travel/historical/romance novels (which are almost always shelved with the romances, but are leagues beyond any of those execrable Harlequin throwaways), The Far Pavilions by M.M. Kaye... I guess that's enough for now.