The Times Difficult Su Doku Book 4

Perfect for the intermediate Su Doku solver in need of a constant supply of challenging puzzles A collection of 200 previously unpublished Difficult Su Doku puzzles of the highest quality from the Su Doku suppliers to the Times newspaper, this book is guaranteed to provide hours of absorbing, brain-stretching entertainment. One need not be a mathematical genius to solve these puzzles; it is simply a question of logic. Each puzzle has a unique solution—and there's no guesswork required.