Black Belt Sudoku by Michael Rios (2005, Paperback)

I wanted a sudoku puzzle book with only hard puzzles. I thought, by the title, that this would fit the bill. However, after doing a few pages, I found that it was not really hard at all - more like middle of the road puzzles. I even went to the last page and did the last one as easy as the first. So, if you want hard puzzles, don't buy this book. It's more like a yellow or green belt.