This is `Nerd Royalty', that's for sure.
Being a long time fan of the online XKCD series, receiving this book from Munroe as a gift really made my day. I starting reading a few of the answers, and ended up reading most of the book in one go. Perhaps that's not how this book was meant to be read... :-)
I think [b:What If?: Serious Scientific Answers to Absurd Hypothetical Questions|25023914|What If? Serious Scientific Answers to Absurd Hypothetical Questions|Randall Munroe|https://s.gr-assets.com/assets/nophoto/book/50x75-a91bf249278a81aabab721ef782c4a74.png|40714465] is a wonderful book for physics and math teachers who are looking to spice up their courses. It could be a great resource for inspiring and fun exercises.
The level of science used in this book is not of a particularly high level, so I believe it can be read by almost anyone. At least anyone interested in the covered material, so perhaps not really anyone. :-)
One point of critique I do have is that Munroe seems to be (involuntarily?) pretty US-centric which shows in various of his answers. It seems to be written for the American public (even though he uses SI units from time to time).