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).
Mathematical Puzzles of Sam Loyd
by Sam Loyd & Margin Gardner (editor), 167 pages, 1959 (Amazon link).
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.