510 books • 53 series
Master of Puzzles - Mini Sudoku 400 Hard to Master Puzzles 6x6 vol.10 (Mini Sudoku, #10)
Master of Puzzles - Anti Diagonal Sudoku 200 Hard Puzzles vol.3 (Anti Diagonal Sudoku, #3)
Master of Puzzles - Anti Diagonal Sudoku 200 Master Puzzles vol.4 (Anti Diagonal Sudoku, #4)