Skill Builder Sudoku: Hard to Expert

Build up your sudoku skills from easy to expert! In this three-book series, each book helps solvers build their skills to get from one level to the next. Puzzles in Hard to Expert are the most challenging and will build on the skills learned in the second book, Medium to Hard. Each new technique (such as swordfish and grid coloring) is introduced gradually, giving solvers time to fully master each skill as they progress to complete sudoku mastery.