76 books • 2 series
Sudoku Book 400 GIANT Puzzles, 100 Easy, 100 Medium, 100 Hard and 100 Extra Hard (Sudoku Book Challenger, #62)
Sudoku Book 1,600 Puzzles, 400 Easy, 400 Medium, 400 Hard and 400 Extra Hard (Sudoku Book Challenger, #44)
Sudoku Book 400 Giant Puzzles, 200 Hard and 200 Extra Hard (Sudoku Book Challenger, #61) (Sudoku Book, #57)
Sudoku Book 400 GIANT Puzzles, 200 Easy and 200 Medium (Sudoku Book Challenger, #59) (Sudoku Book, #55)