This book systematically explains how puzzles test different types of mental functions; memory, verbal, spatial, logical, abstract, perception, listening, motorskill, time estimation, emotional, mathematical, and creativity. The reader is encouraged to solve a variety of puzzles that illustrate each of these mental functions. They are fun, and some are more challenging than others. Each person is different; you might find spatial puzzles more challenging than verbal, while I find just the opposite. The author explains just which parts of the brain are used to solve each type of puzzle, and he logically explains why some types of puzzles are more difficult than others. He gives some evidence that practicing puzzles like these can help improve one's thinking abilities, and reduce mental deterioration later in life. This book is an easy read--and lots of fun!