Depending on what you mean by critters, there are a couple of options for good picture books.
The Reef Aquarium Vol. 1 and 2 are very good books with very good illustration of most fish and corals, as well as anenomes, shrimps, and crabs. The modern Coral Reef Vol. 1-3 are also excellent books, which have more pictures of inverts and things not found in most lfs, like parasites and smaller critters that tag along with your lr and what not. All of the books mentioned above cost about 60 dollars each through mail order or internet, slightly higher most likely at our lfs. Check your local used book store for books on saltwater aquariums. While a lot of the books are outdated, most of the species still have the same names, and photos rarely change so you can get some good bargains on books that are maybe 5 or 10 years old (I got a great book on aquarium corals thats about 15 years old. While most of the information is outdated, at least I know what species everyone is talking about and it only cost me 4 dollars).