Killer Sudoku is a very popular variant of classic Sudoku that adds some new challenges. These puzzles have more going on and can be extremely satisfying to solve. Once you try them, you'll find it very hard to go back to boring plain old Sudoku! This book has 360 puzzles, in order of difficulty ranging from Tough to Insane, using the same grading system as my puzzle website, Krazydad.com. Each puzzle has a single, unique solution. The puzzles are arranged 4-per-page. If you find them too small, check out my LARGE PRINT Killer Sudoku books, which have one large puzzle per page.