Get stuck in to this huge book containing 1,500 extra hard Sudoku puzzles. Sudoku is an entertaining and relaxing way to increase concentration and focus and promote calmness. You choose how challenging you want the puzzles to be. You don't have to complete a puzzle in one sitting, so it's great if you are short on time. Solutions to all the puzzles are printed at the end of the book. Four puzzles per page, 506 pages, 8.5" X 11".