The Ultimate Mental Challenge Author:Robert Allen, Mensa This is the biggest and toughest collection of riddles, word games, number puzzles, mazes and logic problems that the boffins at Mensa have ever produced. So put on your thinking cap and have some fun working these out. These puzzles are by no means easy, and if you can work them out you may be a candidate to join Mensa--the internationally famo... more »us high IQ society.« less