This book make a fascinating read. It is written almost as a hacker's notebook, detailing how a system is targetted and then attacked. Fortunately the book didn't scare me, instead it did reassure me as I was aware of most of the techniques discussed. But the value lays in the way that the book is a summary of all those thousands of web pages discussing vulnerabilities and hacking tools. The book is less than 500 pages yet still covers the pre-amble to an attack and the major weakness (and how to exploit them) of Win 9x, NT 4, Novell and Unix along with other sections on Windows 2000, network devices, firewalls, web servers etc. Some knowledge of Unix and NT services and TCP/IP is assumemed, but it makes a refreshing change to have a book that isn't 1000 pages of padding taken up by TCP/IP and the history of the Internet (again!).