What If? deals with the absurd questions that Mr. Munroe receives on a section of his website, which is primarily known for hosting his webcomic XKCD. Questions include what would happen to you if you started to rise at the rate of one foot per second and what would happen if the Moon disappeared.
While the questions themselves are absurd, Mr. Munroe works through the logic and maths in a serious way, which results in some surprising insights. His trademark irony and delightfully witty foodnotes make for a very enjoyable read.