When "Network Intrusion Detection" is made into a big-budget Hollywood movie, I see Harrison Ford starring in the Stephen Northcutt role. He's experienced and more than a little hard-bitten, he has no patience for the foolish and the ill-prepared, but he really knows his stuff. Plus, there's a gleam of playfulness in the way he tackles the bad guys. Think "Indiana Jones and Back Doors of Quake."
Seriously, Stephen Northcutt is a good writer. He's been there and he's done that, and this book is the summary of what he's learned so far about detecting and countering breakins to a computer network. The book is quite current, documenting exploits as recent as early '99, which is both a plus and a minus. The plus is obviously the freshness and relevance of the content, the minus lies in the somewhat unpolished nature of the book, no doubt an artifact of speedy publication (typos abound, and organization could be improved).
However, on balance, I'd recommend this book to anyone with an interest in computer security. It could also serve as an introductory textbook on hacking into networks, as Mr. Northcutt surely realizes.... But dark hackers already have their own "apprenticeship" system, as he points out, whereas the white-hat community needs books such as this for training analysts.