There are many books on knots. I believe this one punches well above its weight. It's the best knot book I've come across by far.
* Love the selection of knots, and there's a good number to study, too (80+)
* The book has a fantastic primer on knots (seriously, I learned a bunch) and I found the subsequent organization of the book to be really well thought-out. Browsing the selection of knots is really enjoyable, not tedious. It's hard to overstate how nice it is to have each set of knot-typing instructions to start at the _top_ of the page, instead of one following after the other, jammed as tightly together as possible. Makes it so much easier to quickly reference knot information. Which is why I really think this book lives up to it's claim as a 'field guide'. If you want to take this book out with you, it really is a handy / practical reference.
* Speaking of being a practical reference, the book's physical format is perfect; the book falls open and _stays_ open, so you don't have to manage a book that wants to close while you practice a knot...
* The book clearly identifies key qualities of each knot: 1) how hard it is to tie 2) how hard it is to _untie_ 3) what its intended purpose is (holds weight, great for bundling up things, _not_ safe for holding weight, etc.) 4) safety issues (e.g. don't pull in this direction, otherwise knot fails) 5) how it responds to weathering (e.g. whether or not being soaked compromises knot) and more ..
Loved having this book on hand while getting a ham radio antenna in place (30 ft up in a tree). The knots I ended up using have been hard workers and yet, still easy to work with. This book helped me find the perfect ones : )
In short, the book serves as an excellent, practical, well thought-out, and fairly thorough reference. Knots are hard-workers and good friends. If you're interested in learning more about them, this is a great guide that will help you get started while also giving you plenty of reference material to work with as you become more experienced.