Crossword Puzzles->Difficulty->Challenging

Scorchingly Hard Fireball Crosswords: 45 Ultra-Tough Puzzles

The Big Book of Hard Daily Crosswords

Killer Thursday Crosswords

New York Times Sunday Crossword Puzzles Volume 31: 50 Sunday Puzzles from the Pages of the New York Times

The New York Times Sunday Crossword Omnibus Volume 9: 200 World-Famous Sunday Puzzles from the Pages of The New York Times

The New York Times Feisty Friday Crosswords: 50 Hard Puzzles from the Pages of The New York Times

The Crossword Connoisseurred/

Superhard Crosswords to Keep You Sharp

Sunday Delight Crosswords: From the Pages of the New York Times

New York Times Sunday Crossword Puzzles

New York Times Sunday at Home Crosswords: 75 Puzzles From the Pages of The New York Times

Sunday Crossword Puzzles: 50 Sunday Puzzles from the Pages of the New York Times

Simon & Schuster Mega Crossword Puzzle Book #8

Lazy Weekend Crosswords

Simon & Schuster Super Crossword Puzzle Book #11

Go Games Crosswords

New York Times Sleepy Sunday Crossword Puzzles: 75 Puzzles from the Pages of the New York Times

The New York Times Hardest Crosswords Volume 1: 50 Friday and Saturday Puzzles to Challenge Your Brain

Weekend Retreat Crosswords

New York Times Sunday Crossword Omnibus, Volume 7: 200 World-Famous Sunday Puzzles

The New York Times Stress-Free Sunday Crosswords: From the Pages of the New York Times

The New York Times Double Shot Crosswords: 150 Challenging Puzzles

The New York Times Simply Satisfying Crosswords: 150 Easy Puzzles

New York Times Sunday Crossword Puzzles Volume 32: 50 Sunday Puzzles from the Pages of The New York Times