New York Post Difficult Su Doku: The Official Utterly Adictive Number-Placing PuzzlePaperback, 1 July 2006

200 New Difficult Puzzles -- They Are Not Going to Be Easy But You Are Ready

Su Doku, "the crossword without words," comes with a warning: it is seriously addictive. You don't need to be a mathematical genius to solve these puzzles; it is simply a question of logic and a little patience.