I got this book as part of a "Buy something and get this half price deal" - to be honest I wasn't expecting much but thought what the hell. After reading both over the last few weeks I can't actually tell you the name of the first book I bought that this came with, such was the depth this had to offer.
For anyone interested in a simple attack guide this isn't for you - Gray Hat Hacking explores much more complicated subject matter going into detail about the ethics of hacking and responsible disclosure along with the means of doing it properly. If you are working in or touching on IT security this book is a must have - the depth of knowledge is excellent as are the code examples.
If you are new to security or indeed have become a software engineer in only the last few years this book goes back to security fundamentals for good coding, how buffers and machine code actually work. For me as a professional programmer of over a decade, even though I was taught this stuff it has re-awakened me to it and has sharpened up my coding practices as well.
This book is full of stuff and will be the one on your shelf afterwards with loads of post-it notes hanging out the side and plenty of dog-eared pages.