How to Cut a Cake, and its predecessor Math Hysteria, are great books if you are interested in recreational mathematics and are not a mathematician but have a decent background in mathematics. The book has fewer topics than Stewart's Cabinet of Mathematical Curiosities, but they are discussed much more deeply. They are also not so well known, but they are certainly highly interesting. There are two chapters on how to cut a cake so that everyone thinks that he gets a fair share, a chapter on different ways to tie your shoe laces and how long the laces have to be, a chapter on packing circles, a chapter on how the shuffle a pack of cards, a chapter on tangled phone cords, and many others. If you want to know more of the topics in the book, it even has a list of references for further reading.