Facebook: The Missing Manual is an interesting idea. For those who came of age in the internet age, most aspects of Facebook are very obvious - it is, after all, designed to be a user-friendly social networking site. Like many computer programs, though, the basics may be simple, but the deeper features can be complicated, or, at the very least, not intuitive to all people.
This Facebook manual is clearly written and well-organized, with plenty of images to guide the reader through the many options available to you through facebook. The most important, by far, is chapter 13, which reviews privacy settings. If you have any doubts about how to protect your privacy, this should be one of the first things you review.
Facebook: The Missing Manual has one fault, though, and it is due to the nature of the internet itself. In the blink of an eye, this book can be out of date. Facebook is notorious for changing their privacy policies without warning, and they can reorganize the site and its applications at any time. So, there's a certain immediacy to obtaining this book. I would not recommend this if you want to have it available for the future, but I do think it could be useful if you want to explore facebook as it is now.