Sudoku is a game of pure logic--no guessing or math is involved. These highly addictive puzzles are all the rage. But we know you have mastered the easy ones, so we've assembled 200 medium, hard, and really difficult sudoku to challenge even the most dedicated puzzle enthusiast. We've left plenty of space for scratch work as you try to solve these sudoku. And to give your brain a rest between puzzles, we have included Uncle John's trademark tales. Read about numbers, fads,and other puzzling stories. Then pick up that pencil and give these really hard puzzles another go! To help you out, puzzle expert Merl Reagle has provided an introduction to the world of sudoku along with some how-to-solve tips.