Frank Longo

The Nastiest Sudoku Book Ever

2012

Sinister Sudoku: More Than 1,000 Fiendishly Tough Puzzles

2018

Sit & Solve® Double Black Diamond Hard Sudoku (Sit & Solve® Series)

2013

Challenging Thursday Sudoku (Sudoku (Sterling Publishing))

2008

The Peaceful Mind Book of Sudoku (Peaceful Mind Puzzles)

2021

Ninja Assassin Sudoku: Black Belt

2012

CosmoGIRL! Games: Sudoku

2007

Cranium-Crushing Friday Sudoku

2008