Sudoku is a very interesting as well as an intellectual puzzle which develops your logical power. It is always an addiction once you start playing Sudoku. The object is to write numbers from 1 to 9 into the cells of the 9x9 diagram, so that each number occurs exactly once in each row, in each column, and in each region. This book contains 200 Mixed puzzles, 4 per page. 50 Easy puzzles. 50 Medium puzzles. 50 Hard puzzles. 50 Extreme puzzles. We are sure you will find these puzzles offer an entertaining yet effective way to exercise your brain and keep your mind sharp. All puzzles have been checked to ensure there is only one valid answer. Find more pencil puzzle books on Brainy's website www.BrainysLogicPuzzles.com