Ten years before volume 44, Stefan Heine published the world's first killer sudoku book in this series! Since then, almost 4,000 killer sudokus have appeared in Heine's puzzle library, but true fans can never get enough. A challenge for the good and relaxation for all experts - that's how "hard to very hard" is described - that's what this book is all about. 500 high-quality puzzles in four closely graded difficulty levels.