Honestly, 90% of the "hacking" books and resources out there are junk. While they may give you insight into how script kiddies work, most don't go much further than that.
The only true way to understand computer security is to understand systems (software and/or hardware in some cases) very thoroughly. In wholly understanding a given system, you will also be able to identify its weak points and vulnerabilities.
Seeing as how you have a CS degree, you're (hopefully) not afraid to dig into code. Take a look at some OS software and look for potential vulnerabilities (SQL injection attacks, buffer overflows or any other category as listed in the OWASP vulnerability category list).
Other good resources are:
Of course, to keep abreast of the most recent developments, you'll want to get yourself onto the Bugtraq mailing list.
Having said all that, it's been quite some time since I invested any time into security-related matters, so there may be other resources that I'm not aware of.