This isn't your average, run-of-the-mill "draw a circle, then draw some lines, then draw some more lines and you've drawn a puppy" how-to book. It doesn't talk at length about brush strokes or what kind of pencil to use.
This book is something different. Instead, it *explains* how to draw animals so that you understand what you're doing and why. It gives tips for remembering proportions and anatomy (e.g. "[the distance between the eyes of a domestic cat is] 1 1/2 eye's width"). And it illustrates them with lots of examples Every one of the 120 pages is jam-packed with content: examples, explanations, tips and tricks.
Where it simplifies animals into basic shapes, it isn't to give you a step-by-step instruction to just copy the picture that's in the books. It's so that you understand what you're doing better; you get the bigger picture of what the animal's shape is -- and how it bends and moves and so on -- before adding the details.
It goes through each different part of the animal -- the feet, legs, ears, eyes, noses -- and gives examples from each different animal species in side-by-side comparison. This way, you can a) really see how contrasting different animal species are, b) learn to draw each part one by one in easy-to-digest chunks, and c) learn common themes and similarities between animals (which can greatly help in understanding how to draw them better).
It then spends a few pages for each species -- cats, lions, tigers, other felines, bears, horses and other equines, elephants, wolves, dogs and other canines, monkeys, etc. -- explaining how to draw that species in detail.
Throughout the book, it also includes wild, less common animals. At the end of the book, there are a few pages devoted to "odd and unusual animals", and also miscellaneous small animals. These last few pages are just examples of many different types of animal (not detailed explanations like the rest of the book), but after reading the rest of the book you will already understand the basics of drawing animals, so these references would be useful.
This book is great for beginners and advanced artists alike. I would highly recommend it to anyone interested in learning to draw animals.