Put your brain through it's paces with this Brain Gym book of 1,000 Sudoku puzzles, containing 500 hard and 500 very hard difficulty. 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. Solutions are printed at the end of the book. 4 puzzles per page. 8.5 by 11."