O'Reilly have a new book out: Network Security Hacks. It is a really good book (I read it on Safari myself). There are one hundred tips in there, each describing one important point related to security. Not that it affects my judgment, but hack #93 describes how to use mod_security as a Web application intrusion prevention tool. It's no wonder hacks books are such a success. People don't want to read long books any more. Here, on around 300 pages you get the essence, easy-to-swallow, byte-sized knowledge. You can quickly browse through the table of contents and read what you like immediately, remembering where to turn the next time you have a problem. BTW, there are five sample hacks available for download right now.