Vellum
What was at least an interesting idea to begin with soon spiraled into a hard-to-follow novel with no cohesion or consistency. I finally gave up around two-thirds of the book and never picked it up again. This book was a piece of garbage. The worst part was that it had so much potential but failed to live up to it.

The Years of Rice and Salt
Again, an interesting idea looking at a possible alternative history in which the Plague wipes out Europe and most of it doesn't survive leaving China, India, and Africa (if I remember correctly) to continue their expansion and growth into the New World rather than the Europeans.
The book went from interesting to downright boring in no time flat. I forced myself through to the end but I found more enjoyment from the fact that I had finished and would never have to turn another page rather than from the story. No one should waste their time with this piece of junk. Sadly, it still remained highly recommended on WOT. I have no idea why, it sucked.