I recently received copies of Apache Security (AS) by Ivan Ristic and Preventing Web Attacks with Apache (PWAWA) by Ryan Barnett. I read AS first, then PWAWA. Both are excellent books, but I expect potential readers want to know which is best for them. The following is a radical simplification, and I could honestly recommend readers buy either (or both) books. If you are more concerned with a methodical, comprehensive approach to securing Apache, choose AS. If you want more information on offensive aspects of Web security, choose PWAWA.
Before I go further, I must mention that Ivan Ristic cites me and my books twice, on pages 2 and 229. While humbling, I tried not to let this fact influence my review.
AS is an extremely well-thought-out book. My favorite aspect of AS is the decision to start with a blank httpd.conf file, rather than accepting the file packaged with Apache and making edits as needed. By building up httpd.conf from scratch, the author shows exactly what components are needed in a very clear manner. This was not the approach used by PWAWA. I would like to see other technical books adopt this teaching method.
AS includes better coverage of several topics which I believe are core to securing Apache. I liked AS' discussion of chroot environments and jails, although the author should distinguish between chroot on Linux or BSD and jail on BSD alone. AS features a whole chapter on proper PHP deployment (Ch 3), and a whole chapter on SSL/TLS (Ch 4). AS devotes another chapter to explaining how to host multiple Web sites on one host (Ch 6), which is critical to many Apache environments. AS' chapter on Web infrastructure (CH 9) also covers topics not found in PWAWA.
AS is also less explicitly Linux-centric than PWAWA. As a primary FreeBSD user, I found AS' approach more applicable to my environment. PWAWA seemed to assume everyone was running Red Hat Linux. It's fine to use a single OS for all examples, but I had to personally identify tools and techniques that would probably only work on Red Hat.
I had very little trouble with any of the text in AS. My main concerns involve Ch 1, where the author spends time on certain security concepts. I would consider the following with regards to threat modeling on p. 5: (asset) what might be compromised; (motivation) why compromise; (vulnerabilities) where compromised; (attack) how compromised; (threat) who compromised you; (risk) threat X vulnerability X asset value. On pp 9-10 the author should also have used the risk equation just mentioned.
Overall, I really liked AS. The book really is about Apache security, so if you are more interested in attacking Apache you might prefer PWAWA. If you want to learn about Web application hacking in general, your best bets are probably Hacking Exposed: Web Applications, 2nd Ed, and Professional Pen Testing for Web Applications. I will read and review those two books shortly.