From the Publisher:
A collection of 200 previously unpublished Difficult Su Doku puzzles?perfect for the intermediate Su Doku solver in need of a constant supply of challenging puzzles
Puzzlers are guaranteed hours of absorbing, brain-stretching entertainment with this collection. One does not need to 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.