Sudoku super-master Frank Longo and mental_floss, the magazine for trivia lovers, bring fans a collection of superb puzzles sure to stimulate the brain. Longo's puzzles are always top-notch, and because these increase in difficulty as the book goes along, they're perfect for helping solvers build their skills. | mental_floss Sudoku by Frank Longo, Spiral Bound | Indigo Chapters