The Mammoth Book of Brainstorming Puzzles (The Mammoth Book Series)

This book is such a workout for the brain that it would be grueling if it wasn't so much fun. Bodycombe has combined puzzles involving words, numbers, observation, technical reasoning and lateral thinking into a series of mental obstacle courses. They're designed to be timed trials, so you can race against the clock or simply work through for the sheer joy of it. Some are easy and some are killers, but they're all a bit more difficult when the clock is ticking. Each puzzle is marked to let you know which part of your brain is about to be challenged.