An amazing book. This one wastes no time with a long pre-amble or justifying why you'd need to know how to pen-test; it just tells you what you need to know. You're sniffing wireless traffic right from the start, injecting packets by page 40 or so, and then you're off spoofing MAC addreses, cracking WPA (even shared authentication), and doing man-in-the-middle attacks.
This is not a book that explains a lot of theory and then expects you to figure out how to apply it. It's a finely-tuned set of clear, intentional tutorials that explains how to use the tools, how to get results, and then explains what happened and why. It covers some of the basics (like ifconfig, iwconfig, ping, and a little bit about packet specifications), and then moves on to the heavy-lifters like airmon, aireplay, airodump, wireshark, and others.
While all of these tools have tutorials and manuals online, the way they work together is seldomly explained, and even more rarely are they explained with the clarity and focus of this book. The situations the book covers are realistic wireless network setups that you'll find at businesses, cafes, and homes. There are screenshots on nearly everypage, so it doesn't just explain what to do - it actually shows you.
If you're completely new to pen-testing, this book is where you should start. You should try to learn at least a little bit of Linux before delving into this (but you should be learning that anyway) but this book doesn't assume that you are a pro. It guides you through all of the basic essentials, such as setting up a pen-testing lab environment (configuring your access point, making sure your wireless card is open enough to be configured, and so on), and even how to install Backtrack Linux itself. You will need a good lab environment to use this book effectively, so make sure you have access to a router, two laptops with wireless cards (one to use and one to be the victim), and a usb wireless card to perform packet injection (the book recommends the Alfa AWUS036H).
All in all, whether you're learning this stuff because you're angry at the world and want to mess up wireless networks or because you're a sys admin and need to protect your network from intruders, this is easily the best book on the subject I have found. Too many books on this topic assume that the reader is a "security professional" and uses jargon and lingo without explaining anything. This book sits down with you, gives you the information you need, and you get the results that you wanted. Considering that courses from Backtrack's website start at around $750, this book feels like a hack in itself.