31 books • 4 series
Book #1: Cryptogram Book
Book #2: Number Search Puzzle for Adults
Book #4: Sudoku Medium to Hard
Book #7: Hard Sudoku Book
Book #8: Hard Sudoku Book Gift For Dad
Book #9: Hard Sudoku Puzzles
Book #13: Sudoku Puzzles Easy Medium Hard
Book #1: Sudoku Puzzle Medium