It's practically required reading where I work.  It was one of those books that made me dust some cobwebs off my brain.  I was truly impressed.  It is a little down in the weeds for what most people think of as hacking (as compared to say "Hacking Exposed") but it doesn't leave you guessing about what's going on behind the scenes.

I was proud to find that I was finding most of the vulnerabilities in the (admittedly simplistic) C code as it was being presented (before it was discussed).  Anyway, I'd recommend the book to anyone interested in the field.