This is a great book for any administrator who has servers or hosts available to the internet or outside world beyond their own network who don't have expensive hardware firewalls in place to handle traffic, routing, etc.

With the book covering from the basics of knowing iptables and the types of detections, it goes into more depth of network layer attacks, transport layer and application layer attacks. All of these cover great details and how to defend against such attacks.

From this point on, it starts to cover psad, it's features, what can be done with psad deployed in your network and how to set it up to notify and auto respond to potential attacks, basically creating iptable rules to block suspicious traffic that is hitting your server or hosts.

It goes on to cover deploying fwsnort, for further detection and protection.

All around this is a great book and before I can say I obtained this book, we were already deploying psad in our own environment. Having a handy reference now makes things easier with setups and configurations explained in simpler terms without having to refer to online documentation or man pages. Everyone likes examples.