A tossup between books 7-10 of the Wheel of Time series. I gave up half way through book 10 and resent the time that I wasted on the series. 20 years later I still recall the desperate hope that the next chapter/book would advance the storyline, only to be greeted with more subplots, stupid things happening because of characters inability/unwillingness to communicate, and overly verbose descriptions of every little thing.

I hear the final books, written by a different author, were much better.