What If? Serious Scientific Answers to Absurd Hypothetical Questions
by Randall Munroe
By the writer of the webcomic xkcd, this book follows the same idea: use hard science as humour. Munroe doesn't dumb it down, either. The concepts are challenging.
In this book, he takes reader submitted questions and examines what would happen if: a baseball were thrown at near the speed of light; what would happen if tried to use the kick-back of a machine gun a jetpack; what if you turned your hairdryer on to the highest setting, but 1000x hotter?
It's funny and it doesn't use too much jargon so it should be easy enough to understand even when tackling some pretty high-level physics.