I think I have a new record holder for the book that's taken the longest time for me to finish. I began reading Stephen Colbert's I am America the day it was released, that was roughly 4 months ago. I've been reading the book in single page chunks every other day or so. I don't think this was quite the intended way to go through this book, but it held up even in my staccato reading of it.
If you're already a fan of Colbert's from his show, then this book is not going to surprise you in any way. The entire book reads like an extended one of Colbert's Word segments, with footnotes filling in for the show's graphics. If you weren't a fan previously then this book serves as a superb introduction to his brand of razor sharp satire. Just be prepared because Colbert doesn't spare a single potential target for his mock-conservative sense of humor. But if you're willing to have everything you hold sacred ridiculed (and brilliantly at that) then you will love this book.