Martin Gardner is, with no doubt, the relentless champion of mathematical recreations. He had a column in Scientific American for years and years where every time he posted another puzzle or trick with numbers/geometry/probability/cards/games etc...
Gardner released a few collections of these articles as books. This book is one of them.
You can't really say anything bad about a book like this - the articles have withstood the test of time, each causing Gardner to wade through thousands of letters from avid readers. They are very interesting to the puzzle/math inclined, and sometimes quite mind boggling and enlightening. A lot deal with geometry and various related games, but topics range from pi, number theory, probability, infinite series to chess, checkers, reversi, numerous card games and dozens of puzzles. The puzzles range from very easy to very hard, which is nice and gives you a challenge on various levels.
I've been reading a few pages from this book every day, on my way to work. Maybe this is why I got a somewhat sour feeling... These kinds of books - collections of stuff, are not ones to be read sequentially from the beginning to end in a short period of time. If so read, they start to look repetitive and boring. Another trick with squares, another 9 puzzles chapter, blah blah blah. Such things are BEST in their original form - weekly/bi-weekly/even monthly articles. Once in a long period, you open the magazine and can spend a hour or two reading and contemplating a new article, but only in a period. Doing it continually for many days is actually quite boring, though the topics are delighting.
So, a couple of important conclusions: First, this kind of books is great, entertaining and interesting. Especially from the big guns, such as Gardner and Dewdney. Second, they should be read SLOWLY. I.e. make time for once chapter a week. Granted, it will take a year to read a book, but this way you gain the most from it and get to really exercise your brain, instead of getting quickly bored and wading through answers to the puzzles w/o spending 3.14 minutes to think about them.