Longest book(s) I've ever read was the Wheel of Time series.  Actually, I didn't read the whole thing.  I read the first book, which ruled, the second was pretty good, the thired was ok, the fourth was pretty good but slow, and I got halfway through the 5th before I realized......
What a fucking waste of time these books are.  I mean, what the fuck, he's doing 13 fucking 800 page books.  How the hell can someone keep reading these Fantasy books?  They have no goddamn substance!  They're just a story, which is cool and all, but if you're gonna dedicate yourself to reading THIRTEEN HUGE ASS BOOKS, you CLEARLY have no life whatsoever.  I got halfway through the 5th book and said to myself.. "Wow, I simply dont care about what happens enough to subject myself to reading all this shit." 
What a complete waste of time.  I'd rather read something I can get something out of.  Goddamn.