Black Belt Sudoku
Billed as “super-tough sudoku puzzles”, Black Belt Sudoku is a collection of 300 sudoku puzzles. From the back cover:
Created in the United States, these intriguing conundrums were originally called Number Place puzzles. Their recent rise in popularity began in Japan, where the name translated as sudoku. Here we’ve indicated the skill level necessary to complete each sudoku book in this series in the same way Japanese karate levels are ranked: by different colored belts. This is the Black Belt volume, filled with puzzles that will provide a sly, absorbing test for even the best, most proficient experts.
Either I’m a much more accomplished sudoku solver than I think am, or these puzzles are a little easier than billed. If I were you, I’d assume that the latter is the more accurate description.
However, having 300 puzzles in one normal sized book has been great. I’ve been solving puzzles in this book for over 3 months now, and still have about 60 puzzles to go. Additionally, having so many puzzles of comparable difficulty has allowed me to experiment with some different puzzle-solving strategies. While the puzzles haven’t been as challenging as I’d anticipated, I’ve still enjoyed them.
I also enjoy Will Shortz books, such as Sudoku Easy to Hard. The collection of 25 easy, 25 moderate, 25 hard, and 25 challenging puzzles are great. As far as difficulty, the “challenging” puzzles are definitely more difficult than the black belt puzzles.