Will Shortz Presents The Huge Book of Hard Sudoku: 300 Challenging Puzzles

Will Shortz Presents Survival of the Fittest Sudoku: 200 Hard Puzzles

Will Shortz Presents Surrender to Sudoku: 200 Irresistibly Hard Puzzles

Will Shortz Presents Hard Sudoku Volume 2: 200 Challenging Puzzles

SUDOKU Large Print Puzzle Book for Adults: 200 HARD & VERY DIFFICULT Puzzles (Puzzle Books Plus)

500+ Hard Sudoku Puzzles for Adults: Sudoku Puzzle Books Hard (with answers)

Sudoku Puzzle Book, 600 Puzzles, 300 MEDIUM and 300 HARD: Improve Your Game With This Two Level Book (Sudoku Puzzle Books Champion Series)

Will Shortz Presents Mind-Melting Sudoku: 200 Cranium-Crushing Puzzles

Beyond Black Belt Sudoku: If you have to ask, it's too hard for you. (Martial Arts Puzzles Series)

Will Shortz Presents Hard Sudoku Volume 1: 200 Challenging Puzzles