33 books • 40 series
Sudoku 204 Very Easy to Easy Puzzles
Sudoku 390 Very Hard Puzzles
SUDOKU 126 Hard to Extreme Puzzles (126 Sudoku 9x9 Puzzles: Hard, Very Hard, Extreme, #2)
SUDOKU 378 Easy to Hard Puzzles (378 Sudoku 9x9 Puzzles: Easy, Medium, Hard, #2)
Sudoku (120 Sudoku 9x9 Puzzles: Medium, Hard, Very Hard, Extreme, #2)
Sudoku (126 Sudoku 9x9 Puzzles: Medium, Hard, Very Hard, #2)
Sudoku
Sudoku (396 Sudoku 9x9 Puzzles: Very Hard, Extreme, #2)