SUDOKU Puzzles - Hard to Very Hard: Puzzles + Solutions

15 Minute Speed Sudoku - 175 hard sudoku puzzles.: sudoku,puzzle,hard,difficult,gift

Only Hard Sudoku: 400 Challenging Puzzles

Chronicle Books COR

Sudoku 3: 200 Puzzles: Hard to Extreme

The Must Have 2018 Sudoku Puzzle Book: 2018 sudoku puzzle book for 365 daily sudoku games. Sudoku puzzles for every day of the year. 365 Sudoku Games - 5 levels of difficulty (easy to hard)

Clarity Media

25x25 Sudoku: 100 sudoku puzzles complete with solutions