Mensa Absolutely Nasty Sudoku
If you are finding those "Advanced" newspaper sudokus ridiculously easy, it's time to ramp it up! This is NOT a book for the beginner. Beginning with challenging, the books increase in difficulty through the levels. Level #1 requires only basic and intermediate techniques to solve; Levels 2 and 3 add more advanced techniques; by Level 4, puzzles require multiple advanced techniques. However, these are all solvable by logic puzzles; none of them requires guessing to complete. So, after cutting your teeth in Mastering Sudoku Week by Week, you can practice some pencil-biting in this series. All answers are included in the back of the book.