If you're interested in rendering, more in general, there's Principles of Digital Image Synthesis by Glassner. This is probably the only book(s) I can point out as a standing example out of all I've learned from during the studies in the field. Lots of nice material now out there, of course, but this one is at the core of everything. It wasn't maybe suitable for realtime rendering, but as tech advances - we're getting there. It's even available now online: http://www.realtimerendering.com/Principles_of_Digital_Image... (and damnit I paid a bit over $200 back in the day)
