This is the latest collection of 200 previously unpublished Difficult Su Doku puzzles - perfect for the intermediate Su Doku solver in need of a constant supply of challenging puzzles. You are guaranteed 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 5 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.