Simon & Schuster Mega Crossword Puzzle Book Series: This series offers a collection of challenging crossword puzzles with a wide range of difficulty levels. They are known for their variety and large format. Will Shortz Presents... series: Will Shortz is a renowned crossword editor for The New York Times. He has published several crossword puzzle books with various themes and difficulty levels, including the "Will Shortz Presents KenKen"...