11 books
Sudoku Fiendish, Volume 2
Sudoku Fiensidh, Volume 4
Sudoku Fiendish, Volume 5
Sudoku Fiendish, Volume 3
Sudoku Extreme, Volume 1
Sudoku Extreme, Volume 5
Sudoku Extreme, Volume 2
Sudoku Puzzle, Volume 3
Sudoku Puzzle, Volume 4
Sudoku Puzzle, Volume 5
Sudoku Puzzle, Volume 1