Carol Vorderman's How to Do Extreme Sudoku, Paperback

And once you're ready to flex your new Sudoku muscles, 300 brand-new, hand-crafted puzzles await you: from regular Sudoku puzzles ratcheted up to severest of difficulty levels to new favourites such as Killer Sudoku, Squiffy Sudoku and Sudoku 16. You may be a Sudoku Master, but will you be able to master Extreme Sudoku?