No one reworks a solved puzzle, making puzzle books perhaps the most disposable of all books. However with its aqueous (water-based) coating and biodegradable soy inks printed on recycled paper, The Green Book of Sudoku 2 wraps 200 challenging and enjoyable Sudoku puzzles in a disposable package that minimizes its effect on our environment. A puzzle can only be solved once, making puzzle books perhaps the most disposable of all books...