I've found these 4 books but not sure what to pick. I took 1 security class 2 years ago (college), so I have a basic understanding of web security. But, I would by no means call myself an expert in security techniques.
Web 2.0 Security - Defending AJAX, RIA, AND SOA
Developer's Guide to Web Application Security
The Web Application Hacker's Handbook: Discovering and Exploiting Security Flaws
All can be found on amazon.