I just finished Guns, Germs, and Steel: The Fates of Human Societies
. It only took me 3 years reading it on and off. It is a fascinating book that covers a remarkable sweep of knowledge and history. I had promised myself I would finish it before reading anything on my new Kindle and I didn't relish the idea of carrying it, yet again, on another airplane only to make minimal headway.
I definitely recommend it and would make sure you are pretty dedicated to powering through it. This feels like I've definitely accomplished something.