George Martin's A Dance With Dragons (no spoilers)

A Dance With Dragons is easily the worst book in George Martin's A Song of Ice and Fire series. But I read 950 pages in a week, and often gave up sleep to do so, so it would be silly to call the book bad.

In retrospect, the flaws of the book were trumpeted by Martin himself. A third (or more) of the book is content that was meant to be included in A Feast for Crows. But that book ran too long, so the content was saved for this. In other words, it's b-material that never deserved to be its own book. Another third of the book was frequently described by Martin as the "Meereenese Knot" - - an inescapable plot hole he had worked himself into. His difficulty in solving that "knot" was the reason the book was so famously delayed. What he really needed was someone to tell him that the Meereen portion was trash and should be completely discarded. (Is there somewhere where he's defended the main character's actions in that part of the book? Because they certainly made no sense to me.)

The last two hundred pages more than made up for the rest of the book, though, and it will be a long, difficult wait for the next book.