Absolutely Nasty Sudoku: Even Nastier - Level 4

Gluttons for punishment rejoice! The popular series of ultrahard sudoku is back. Just when it seemed safe to go back into the puzzle section of the bookstore ... here comes another collection of the hardest sudoku known to humankind. The newest four volumes of this bestselling series range from Level 1 to Level 4, increasing in difficulty as they go. In Level 1, solvers will encounter 242 puzzles difficult enough to make them say, "Wait ... this is the easiest level?" After the book is complete, three more levels await those who are daring enough to continue!