Daniel J. Barrett, Ph.D., has been teaching and writing about Linux, the internet, and related technologies for more than 30 years. Dan has also been a software engineer, heavy metal singer, system administrator, university lecturer, birthday party magician, and humorist.
Linux Security Cookbook must have been one of the earlier O'Reilly books that I purchased. I'm sure I've referred to several of the recipes over the years. In deciding to read this cover-to-cover after all this time, while dated and obviously not comprehensive, it's actually a pretty good security primer for any novice wanting to get familiar with tools used for Linux from a more security-minded standpoint.
This has aged reasonably well since 2003; the main "problem" is that a few of the hardening tips (e.g. source address verification) are now defaults. This is a Good Thing. Otherwise, like most of O'Reilly's Cookbook series: very clear directions for a number of specific tasks that serve as an entry point to more involvement in the topic. Remarkably good for reference when later on you remember "oh, I know I came across a way to do that." The structure makes content per page fairly low, but the utility very high; the ebook's totally the way to go.