Dan Croker has two obsessions - Sudoku and frogs. So he just had to combine his loves and make the Famous Frog Sudoku books. This Famous Frog Hard Series Book contains 600 hard puzzles. There are 4 puzzles per page and a fun and colorful cover that is sure to brighten your day. Solutions are given at the end of the book. More Famous Frog Sudoku series - Beach Bum Series, Bathroom Sudoku, Extra Hard Series, Brain Yoga, Sharper Pencil Series, Giant Series, Take a Break and The Travel Series.