The Times: Su Doku - Difficult

This is a collection of 200 previously unpublished Difficult Su Doku puzzles. It is perfect for the more advanced Su Doku solver in need of a constant supply of challenging puzzles. It is guaranteed to provide hours of absorbing, brain-stretching entertainment. Since the first Su Doku puzzle appeared in "The Times" in November 2004, they have become a phenomenon, with over 4 million copies of 'The Times Su Doku' books sold worldwide. You don't 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. 'The Times Su Doku' remains the original, the best and the market leader. The puzzles are provided by Wayne Gould, the man who started it all.