It's the sudoku collection that's not for the faint of heart. If you're craving the challenge, sharpen your pencil and pit your wits against the Japanese puzzle-makers at the top of their game. In each of these more than 300 handcrafted puzzles, ranked by difficulty from expert to x-treme to ultimate, every move is an adventure, a one-on-one challenge with a grandmaster who delights in elegance, symmetry, and building in the occasional roadblock. But keep going. You'll solve it eventually... you genius!