Welch-Abernathy's presentation style is characterized by conciseness; practically every word and illustration he's included advances his goal of explaining how to administer the software. Once in a while, he'll go so far as to declare something self-explanatory and therefore not document it. This is risky--it's hard to predict what a given reader will find intuitive--but he's done this sparingly. The author's coverage of virtual private networks (VPNs) is particularly praiseworthy. By following his lead, you'll be able to bring up secure links among sites, and understand why the system works. Whether you're reading cover-to-cover in order to learn as much as possible, or using the index to locate the problem-solving trick you need, this book ranks among the best. --David Wall