0Put your brain through it's paces with this Brain Gym book of 500 Sudoku puzzles, containing 250 medium difficulty and 250 hard. We exercise our bodies but our brains need a workout too! Sudoku helps keep your brain healthy and functioning well. Challenge yourself to finish all the puzzles without cheating! This book contains solutions to all the puzzles. 178 pages, 4 puzzles per page. 8.5 by 11".