This book is great! Very understandable, very scalable, very creative, and most importantly full of puzzles that strike a delicate balance of interestingly complex while comprehensibly solvable.
I bought this just the other night because I knew I wanted a puzzle for my next session but I just didn't have the time or energy to come up with one. After pawing through the book for like 15 minutes I found the triangle door puzzle and it seemed perfect for what I needed. I drew up a piece of art (though I didn't need to thanks to the handy appendix handouts) and I was 100% ready to run the encounter.
Several things I really loved: 1) the variety of puzzles on hand 2) their wide-ranging customizability 3) every puzzle has a REALLY USEFUL section of hints and tips you can use to feed your players along the encounter - I didn't end up needing these for the session I ran but I was super glad they were there to rely on if my players got stuck and finally 4) the raising the stakes sections weren't applicable to my low-level group, but they will make this a product I'll return to when I run higher level sessions in other campaigns.
Overall I'd say it's a 5/5 or 9/10. I say 9/10 only because while every puzzle was comprehensible and didn't need more art, it would've been even better if there had been like a solid piece of art or two for every puzzle - I hope that a bigger budget allows for expansion like this in sequel products.
[5 of 5 Stars!]