This book features the following: - 100 puzzle grids - Easy, Medium, Hard and Very Hard level puzzles - Large grids and print font for prevention of eye-strain - History of Sudoku - Keep Your Mind Sharp With Sudoku - Sudoku Rules of Play - The Basic Rules of Sudoku - Answers (all solutions) 25 Easy Difficulty Puzzles 25 Medium Difficulty Puzzles 25 Hard Difficulty Puzzles 25 Very Hard Difficulty Puzzles Did you know the American Alzheimer's Association has endorsed Sudoku as a "brain game" that might help to reduce risk of dementia as we get older?