The subtitle of this book is "A Practical Guide to Configuration, Customisation, and Integration" and it lives up to this admirably. The first few chapters cover what is Spam, where it comes from, how it is sent, and methods used to detect and classify it. All this provides grounding so that by chapter six - Installing SpamAssassin, the reader is well acquainted with the characteristics of spam and how to use SpamAssassin to fight it. There are two sides to a good anti-spam installation: integration with the mail system in use and the configuration of the spam rules. For the former the book provides a step-by-step guide for the most common mail system and should prove no problem as most of these are fairly mature products. In contrast, configuration of SpamAssassin is addressing a rapidly moving target requiring constant attention paid both to the profile of spam and ham the users are receiving, and the type and methods of unwanted email being generated. The book does a good job of covering the topic, but an efficient anti-spam filter requires knowledge of how spam has evolved since the book was published and how it will evolve in the future. Although SpamAssassin is a best-of-breed today, it is a victim of its own success and already the spammers are working out how evade it, so it is possible that the book could suddenly become very dated. Until that happens, this is an essential book for anyone trying to hold back the flood of unsolicited email.