The Gigantic Sudoku Puzzle Book. 1500 Puzzles. Easy through Challenging to Nail Biting and Torturous. Largest Printed Sudoku Puzzle Book ever. All puzzles are guaranteed to have only ONE SOLUTION!
I am a puzzle nut , so when I first got the book as a present , I was hoping for a challenge ,and BOY did I get one ! I also appreciated the extra space for workings. Level 6 is crazy so be warned !  --Marty Greuben