I love this book. It truly is the Holy Bible of Firewalls. At the time the book was written Unix was by far the main platform for Firewalls. Today there are several programs which have ported to NT such as Gauntlet, Raptor, Firewall-1, and more..
Since most people forget that securing you network has more to do with protocols than what OS you run they get cought up in flame wars between Unix and NT - what a waste of time..
If you're a Network Administrator like me then you are Agnostic in your flavor of OS. You use the tools that fit the job.. That's exactly what this book does! It starts out by saying that it's platform independent, although at the time of writing they used Unix in their examples, but whether you are NT or Macintosh it doesn't flippin' matter! By learning what a Bastion host is, a screening router, a choke router, packet filtering, etc. you will clearly learn ALL the most crucial information on network Firewalls.. What more could you ask for? This book TRULY lives up to its name.. My only regret is that I didn't buy it sooner!