Probably everybody has this book. I'll take this book whenever I go to buy or look at new livestock. It gives you a general description about the fish's shape, size, coloration as well as sexual differences if known. Included in the info is the environment the animal needs like ph, lighting and temp. Also it has what the animal eats as well as its social behavior, peaceful, aggressive, etc. The book includes color photographs and gives not only the scientific name but the common name as well.
It's a very well rounded book with lots of good information. I'm on my third one because I keep wearing it out. It's fairly cheap, about 15 bucks or less depending on where you buy your books.
Over all, I'll give it an 8 out 10. If you have to take one general book to the lfs, this is it. However you may need to get a specialize book for marine / reef / invets or freshwater fish.
Get it. Use it. But must of all, be happy with your tank!
phil
Freshwater and Marine Aquarium Fishes 
&&&&For he today that sheds his blood with me shall be my brother.&&&&William Shakespeare
