"The Sudoku Institute Puzzle Book" is a new brand in the highly competitive gaming world. Returning the game to its Japanese roots, this book will feature the aims of sudoku (to broaden minds, increase mental sharpness and train gamers to cope with periods of intense frustration). Where the "Sudoku Institute Puzzle Book" stands out from the others is that the quizzes are grouped in order of difficulty along the lines of martial arts 'belts' - from yellow through all the colours to black and red. The puzzles will range from simple 6 x 6 squares via increasingly difficult 9 x 9 grids to a series of mind-bending 16 x 16. All of these will have solutions provided. However, for those talented and brave enough, there will be a 25 x 25 Red Belt Challenge. Alongside the book, the Sudoku Institute will have a website which will provided even more fiendish puzzles and expand on the Institute brand by selling t-shirts and badges stating 'We've Got Your Number'. - from Amzon