Holmes is a book of logical sudoku puzzles of very difficult levels. The Kakuro levels are 17x17 + 18x18 + 19x19 + 20x20. A chain of Sudoku puzzles with the names: "Sudoku Girus", "Strymko". Book for superior mental support. In addition, there are links to download 500 puzzles. I hope you enjoy this book. Best Regards, Basford Holmes