A fantastic book for computer scientists and mathematicians who love combinatorial puzzles. Many puzzles are algorithmic in nature. I borrowed some of his puzzles for exposition: Fifteen Sum and Ant Collisions, for example.

An interesting puzzle appears on the back cover of the book:

"A large regular hexagon is cut out of a triangular grid and tiled with diamonds (pairs of triangles glued together along an edge). Diamonds come in three varieties, depending on orientation; prove that precisely the same number of each variety must appear in the tiling.

The solution is the picture on the front cover :)

After the success of his first puzzle book, Peter Winkler wrote a second book called Mathematical Mind-Benders (160 pages, 2007).

Sam Loyd was a recreational mathematician who was called "America's Greatest Puzzler" by Martin Gardner. In 1914, Sam Loyd's son published The Encyclopedia of 5000 Puzzles (free, now in public domain). A large-sized (43MB) PDF is available here. Some of the popular puzzlea are available here.

A nice collection of puzzles from Russia, where this book was originally published.