Gluttons for punishment rejoice! The popular series of ultra-hard 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!

About the Author

Frank Longo creates, fact-checks, and edits crossword puzzles, and also specializes in sudoku, having published more than 150 sudoku books. His books have sold more than 5 million copies. His wide array of titles encompasses both standard and variety sudoku puzzles, and includes Beyond Black Belt Sudoku, Way Beyond Black Belt Sudoku, The Nastiest Sudoku Book Ever, Pause for Puzzles: Sudoku for Mindfulness, Sip & Solve Simple Sudoku, Blockbuster Book of Sudoku, Puzzlewright Guide to Solving Sudoku (with Peter Gordon), and Skill Builder Sudoku (with Peter Gordon).