what if? Serious Scientific Answers to Absurd Hypothetical Questions", by physicist and ex-NASA robotics engineer Randall Munroe, the Internet cartoonist behind xkcd (http://www.xkcd.com).
From the back cover:
Humans can't digest the cellulose in paper, but if we could, eating this book would give you about 2300 calories (including the cover). ...
Hidden Feature: The inside of this book has words and pictures. It answers many other important questions, including whether you could jump from a plane with a helium tank and inflate balloons fast enough to slow your fall and survive (yes) and whether you could hide from a supersonic windstorm in Finland (yes, but it won't help).
I started reading the first question / answer, What would happen if the Earth and all terrestrial objects suddenly stopped spinning, but the atmosphere retained its velocity?
I am entertained. I recommend the book (and the on-line comic).