At Crown Books and other ``remaindered'' book sellers, you will find a book edited by Dick Mills that is called The Concise Encyclopedia of Tropical Aquarium Fishes if it's published by Crescent (and Tetra's Junior Atlas of Tropical Aquarium Fishes if it's published by Tetra). It covers all the basic ideas about setting up an aquarium and has descriptions and fair quality photos of over 300 species of fish (the book is not in front of me so can't give you more detail). It's published by Salamander Press in Europe and Tetra (Crescent) in US. (Crescent edition ISBN 0-517-66776-2)
At Tower Books and other ``mainstream'' bookseller chains and larger book stores, you will find Barron's series of translation of German aquarium books, all between $5 and $8, concentrating on specific categories of fish (Killifishes (ISBN 0-8120-4475-4), Cichlids (ISBN 0-8120-4597-1)), or breeding (Ines Scheurman's Aquarium Fish Breeding (ISBN 0-8120-4474-6)), or general aquarium maintenance, or plants. All of these books give a beginner a solid introduction to what and why of the the filtration, water chemistry and so on. Any of these books make an excellent starting point. They don't have very many color photos, which probably contributed to the low price, but have a lot of drawings.
Also near the $10 mark (and a lot less through mail-order), are the Tetra/Salamander series of ``Fishkeeper's Guide To...'' books. They are available at a number of ``normal'' book stores and I recommend ``... Healthy Aquarium'' and ``...Community Fishes'' as the better beginner books. The rest of the series is quite good as well and any one of these books should be a great start.
``The Innes Book'' -- First published in 1935, it is a thick volume that has gone through a dozen publishers and something like 50 editions. The newer ones will probably be a bit more up to date, but the older ones are not bad, either. They range from $2 to $15 and my preference is for the oldest editions. Don't expect the fish names to match the current nomenclature or in some case even the real species -- for the last 40 years ``The Innes Book'' has had a picture of A. filamentosum for their Aphyosemion gardneri.
These are the cheapest books. If you are willing to spend $15-20 (and you better be willing to spend that much on the books if you are go to spend that much on the fish!), the number of books is larger and the amount of information increases.
van Ramshorst's Aquarium Encyclopedia published by HPBooks and sold by Waldenbooks is a translation from Dutch and at $17.95 is among the better ``shopping list'' aquarium books. It is full of very good quality color photos, covers over 570 species of fish, 80 species of plants, all aspects of aquarium design, building, set-up, decor, etc. Not much on filtration, but that's all in the FAQ, so not a big flaw for a USENET reader.
Crown Books used to sell The Living Aquarium, a translation from Swedish published by Crescent Books. It's close to $20 and does not have descriptions of too many species, but has a lot of detailed diagrams, goes into the black arts of filtration and lighting and attempts to cover cold water and tropical fresh water, cold water and tropical marine and brackish aquaria, suggesting the species and decor for them. It also has a section on building aquaria, as all European books seem to.
There are a few exceptions to that rule in the TFH line: Dr. Jubb's ``Nothobranchius'', 2 volumes of Jocher's ``Spawning Problem Fishes'' and Windelow's ``Aquatic Plants'', but they fall into the ``specialty'' category).