Because I wrote a three star review of the first edition of The Book of Pf by Peter N.M. Hansteen, Amazon.com won't allow me to write a review of the second edition. So, I added the following comment to my old review indicating that I think the second edition deserves four out of five stars:
Amazon won't allow me to write a review of the second edition of this book, so I'm adding this comment. I'm pleased to say that I believe the author accepted much of the feedback in my first review as well as feedback from other reviewers. He's improved the book so much that I think it warrants 4 out of 5 stars. He spends more time explaining key concepts rather than simply including them in the text. For example, the author introduces features like macros (p 18) whereas in the first edition he just started using them. The book is also fairly up-to-date, with coverage of OpenBSD 4.8, FreeBSD 8.1, and NetBSD 5.0. Reading how to use Pf on all three platforms was very helpful. One request for a future edition is to include more "tips and tricks" that an experienced firewall administrator is sure to have. For example, when working remotely on a firewall ruleset, what methods does the author use to test configurations and ensure that if he makes a mistake he isn't locked out of the system? Finally, I think this book is a fine companion to PfSense: The Definitive Guide by Buechler and Pingle.