Mathematical Magic Show by Martin Gardner
How do you move two matches - and only two - to new positions, so that the glass is reformed in a different position, with the cherry outside? This is one of those rare puzzles that can be solved at once if you approach is correctly, but intelligent people have been known to struggle with it for 20 minutes. The author provides the solution. The treats in this book range from Moebius bands to coin and card trickery, from finger arithmetic to the post-Ticktacktoe game of Tri-Hex.