"What If? Serious Scientific Answers to Absurd Hypothetical Questions" by Randall Munroe

xkcd is a nerdy Internet daily cartoon that is written and drawn by a former NASA "roboticist". The subject matter is all over the map [yesterday's (11/4/14) is about TypographicChemistry], but tends to favor physics and computing. He encourages readers of the cartoon strip to send him outrageous questions, and he supplies outrageous but scientifically accurate responses. Some of the best of these have be come a surprising NYT Best Seller.