106 books • 14 series
Hard X Large Sudoku-Volume 4 (Hard Sudoku, #4) (Sudoku Puzzles Book for Adults with Solutions, #4)
Hard X-Large Sudoku-Volume 2 (Hard Sudoko, #2) (Sudoku Puzzles Book for Adults with Solutions, #2)
Hard X Large Sudoku-Volume 5 (Sudoku Puzzles Book for Adults with Solutions, #5) (Hard Sudoku, #5)