"Aquarium Corals, Selection, Husbandry, and Natural History", by Eric Borneman. The coral-keeper's bible.
Check out the --> "Recommended Literature" section of my site
for some brief reviews on some other books.
I've got a couple new ones I haven't added to the site yet, but they're not necessarily coral-picture specific books ("Coral Reef Animals of the Indo-Pacific" - Gosliner/Behrens/Willims. "Book of Coral Propagation" - Calfo, and "Reef Invertebrates" - Calfo/Fenner)
A couple good sites: