This book contains 500 Sudoku Puzzle Books Hard Extreme For Adults. All of the puzzles inside the book are 9x9 grid. Sudoku rules are easy. Each number 1,2,3,4,5,6,7,8 and 9 must appear only once in each row, column, and region. Complete this puzzle so that every row across, every column down and every region contains the numbers 1 to 9. Each row and each column have only one and exactly one of each of the numbers 1,2,3,4,5,6,7,8,9 Book Features: 500 Sudoku Puzzle Books For Adults Hard Extreme Sudoku puzzles grid size in the book are 9x9 that are played with nine number 1,2,3,4,5,6,7,8,9 An answer key for each sudoku puzzle Puzzles are printed on high quality white paper, paper size 8,5 x 11 inches A simple instructions for beginners Sudoku puzzles are a proven method for enhancing logic skills. As a logic puzzle, Sudoku is also a great brain game. If you play Sudoku everyday, you'll soon begin to see improvements within your concentration and overall brain power. You could reduce your probabilities of Dementia or Alzheimer's simply by solving Sudoku puzzles. By using this selection of sudoku puzzle books you would experience enhanced brain capabilities for example focus, logical thinking and memory. Choose your book today by clicking on the BUY NOW button at the top of this page.