Beyond Black Belt Sudoku: If you have to ask, it's too hard for you.

These are some very difficult Sudoku puzzles, requiring upper-level solving strategies.

Are you a sudoku warrior? Now you have an incredible opportunity to reach elite status and bask in the glory of completing some of the hardest sudoku ever constructed. For diehards only! These incredibly difficult puzzles are handcrafted for the sudoku warrior who dares to go where other solvers fear to tread. So, if you're armed with the highest-level strategies, get ready for the most satisfying fight your life. It's the most challenging sudoku book we've ever published!