Although this is primarily intended to be an illustrated reference guide, it's a surprisingly fun one to thumb through. Part of that is the delight of looking at pictures and illustrations of some truly strange organisms (science fiction writers should really buy this book to see what genuinely alien creatures are like), but also due to the plethora of interesting facts.
I know that when I was reading through the section detailing the Animal phylla, I was struck by how many creatures -- entire phyllums -- get along without even rudimentary brains (or digestive systems, respiratory systems, circulatory systems, or even organs, altogether, in some cases). Likewise I was surprised to learn that only two phylla (including our own) ever developed winged flight.
The sections comprising the non-Animal kingdoms were of particular interest to me mainly for the simple reason that they invariably get little attention from most texts. At best, you'll usally find a chapter dealing with micro-organisms as a whole, and a brief chapter on plants. To see how much sheer diverity there is in just the Fungus kingdom is eye-opening.
I will note that the book does assume a basic level of biological literacy and that it sometimes throws jargon at the reader with little warning or explaination but, as a whole, this is a very accessible work and well worth having on one's shelf.