My favorites books for new SW aquarists are:
The Conscientious Marine Aquarist, by Robert Fenner
Natural Reef Aquariums, by John Tullock (First purchase).
The Reef Aquarium, Vol. 1 & 2 ($$), by Charles Delbeek and
Julian Sprung
Aquarium Corals: Selection, Husbandry, and Natural History by Eric Borneman.
All of these have great information. I recommend any/all of them.
I usually buy through Amazon.com. I don't know about used book sites, but occasionally you can find them on eBay. Just don't go getting an old version. You really want the latest info possible.
HTH,
Ed
[ 07-29-2001: Message edited by: DaktariEd ]