Christmas apparently comes just once a year but if you're a rainbowfish fan, it may well feel like Christmas has come early, with this fabulous book which can be downloaded free!
Rainbowfishes – Their care and keeping in captivity by Adrian R. Tappin offers an excellent reference guide to the rainbows of Australia and New Guinea, with detailed information on their distribution and habitat, collection, and keeping and breeding them in captivity. There are plenty of great pictures, too. If you're a rainbowfish fan, then this is definitely for you.
It's not often you get a chance to download something this detailed for free. And at 400-plus pages, this really is an indispensable guide to these wonderful fish.