The book explains in great detail how to set up and maintain an aquarium, and there's a great section on what to do when something goes wrong or your fish are acting "funny". The information is explicit when detailing procedures, and the author approaches aquarium setup and maintenance with the idea of keeping the fish as stress free (and therefore healthy) as possible.
Many all-in-one aquarium books devote 3/4 of the book to gorgeous fish and aquarium pictures without including much detail on how to keep everything looking (and feeling) that way. The Fishlopaedia doesn't have a lot of pretty pictures, but it does have a wealth of information.