Sudoku Book 400 Extra Hard Puzzles

Sharpen up your mind and improve your memory by playing Sudoku every day. Sudoku stimulates your mind, increases concentration and makes you feel happy by giving you a sense of accomplishment. It is said it can also reduce the chance of developing Alzheimers. This Sudoku puzzle book contains 400 puzzles with a single level of difficulty, so there are no wasted puzzles. There are 4 puzzles per page and solutions are at the end of the book.