This is the best bang-for-my-buck DM purchase I've ever made. The puzzles are basically system-nuetral, and can be easily dropped in to virtually any fantasy setting or dungeon. When I need to scramble to prep for a session (which is always), I can start breezing through these until I find one that seems like a good match, and drop it between the party and their objective.
Just reading through all these is a fantastic exercize in broadening your approach to "puzzles." The next time I design a dungeon from scratch, I may borrow one of these puzzles, or I may use the inspiration I've taken from this book to design my own.
Let's assume each of these puzzles gives a party of four adventurers a half-hour of head-scratching delight. That's two hours of total delight, multiplied by 60 puzzles... that's 120 hours of delight for $5.
[5 of 5 Stars!]