A Hardcore Sudoku Book for the Master Puzzler
These tremendously difficult Sudoku puzzles require complex diabolical and extreme strategies that will challenge the most die-hard Sudoku expert. Not for the beginner or the average leisure Sudoku player. You'll need every trick in the book to tackle these puzzles. Beyond the typical hard level, this Sudoku puzzle book is incredibly challenging but all the puzzles are solvable (with one true solution).