***SPECIAL PRICE down from $19.95 while stocks last*** These books are a modern fitness studio for the brain! A total of 300 diverse puzzles help to keep your mind flexible and train your mental stamina in logical and mathematical thinking. Time and time again, the collection of widely-varied games of mental agility contained in these two volumes will set you new tasks to challenge your grey cells! Accept the challenge posed by these two training programs and discover the fun of finding your own logical path through the puzzle labyrinth!