World's Hardest Sudoku Book: 200 of the World's Toughest Sudoku Puzzles Paperback – May 2, 2016

This is finally the book that has defeated me. I did all the Will Shortz and Black Belt version, all the nasty ones. These a just A new level of hard. Go ahead and buy if you think you need harder ones.

My sister loves her new Sudoku book. So far she’s finding the these hard games challenging as she goes to harder ones.

My brother is a long time user of Sudoku and enjoyed these very much because they were challenging

This is the most challenging sudoku book ever to my black belt husband.

Given as a gift but wasn't too difficult to solve. There were alot of sudoku puzzles.

love this book. Hard. I just finished it. Order two more. I am addicted to this.

Puzzles aren't really that hard but the format/layout has little margins (so if you use them for solving - this might not be the book for you)

a few relatively straight forward but many are quite challenging