Expert Sudoku is an all-new collection of handcrafted puzzles for the expert puzzle-solver. This is the book that challenges skilled solvers and Sudoku-lovers at the top level—every one of the 320 puzzles is rated "difficult." Good luck!
Nikoli is the Japanese puzzle and game company that’s been nurturing and developing sudoku for over thirty-five years. They hold the trademark on sudoku in Japan, and supply 100 percent of the puzzles published in Japanese newspapers and magazines.