9 books
Samurai Sudoku Medium Puzzles - Volume 1
Just Sudoku Multi-Level Puzzles - Volume 1
Samurai Sudoku Difficult Puzzles - Volume 1
Number Fill-Ins - Volume 1
Just Sudoku Easy Puzzles - Volume 1
Samurai Sudoku Easy Puzzles - Volume 1
Just Sudoku Medium Puzzles - Volume 1
Just Sudoku Difficult Puzzles - Volume 1
Just Sudoku Expert Puzzles - Volume 1