Complete Joy of Homebrewing
How to Brew
Designing Great Beers
Radical Brewing
Tasting Beer
Homebrewing for Dummies (yes I'm serious)
Brewing Classic Styles
Joy is a good book, but not as technical as How to Brew. How to Brew has more technical information, but IMO it lacks Papazian's zeal and encouragement. Both will provide TONS of information useful to brewing. I was surprised by the Dummies book as well.
After those three, check out the others and as always look to HBT to provide even more useful and up-to-date information. And check out Basic Brewing Radio and The Brewing Network among others for great audio and video podcasts all about brewing.