Kretchmar is a network engineer for MIT and has gotten a lot of practical experience in managing large networks and unruly hosts. In this book, he imparts a large amount of that experience in over 200 quick-reading, no-nonsense pages. He tells you what a tool can do, how to get it and build it and provides examples of some typical uses. While beginning network administrators will feel comforted that he takes enough time to explain the tools he talks about, experienced ones can safely jump right to his equally well-explained configuration examples without missing anything crucial.
This book read so quickly and was so straightforward that it really inspired me to fix up some areas of my network monitoring that I knew were lacking, but hadn't bothered to fix. In particular, his chapter on Oak motivated me to implement an instant messaging infrastructure (like one he mentions using at MIT) to receive event notices quickly and without dependence on e-mail. While it's no bible (my staple, the Unix System Administration Handbook, is over 800 pages), this book provides a great start on quite a few great tools -- many of which I plan to investigate soon.