Su Doku (The Times, Book #1)

Since it first appeared in The Times in November 2004, Su Doku has attracted a huge following. Many thousands of readers either start or end their day by tackling 'the crossword without words' as it has been described. Here is a collection of 100 previously unpublished puzzles. They are arranged according to difficulty: starting with the easiest and ending with the fiendishly difficult.