200 New Difficult Puzzles -- They Are Not Going to Be Easy But You Are Ready Su Doku, "the crossword without words," comes with a it is seriously addictive. You don't need to be a mathematical genius to solve these puzzles; it is simply a question of logic and a little patience.
This is a great book. I have taken it with me everywhere I went on vacation for the last few years. It has been to Vegas, Duluth and Massachusetts. These are "difficult" puzzles, but not ones that you stare at for hours without finding a single number.
I do the Star Tribune puzzles on a weekly basis. The Trib rates the puzzles on a 7 star difficulty rating. Monday being a 1 star and the easiest, and Sunday being a 7 star and being very difficult. The New York Post probably has a different rating system, but I think these puzzles were between a 4 and 5 star (trib) rating with a few 6's thrown in.
Great book, not much "re-readability". However is you bought a new copy, you wouldn't remember the solutions to the puzzles if you re-did them.