I can see by the review below that if you're looking for a quick route to being the next Darren Brown this book might be less than expected but then I don't think one book will fast track you anywhere in that direction, especially if you only read half of it! But if you are someone really interested in facial perception this book is invaluable. It explains all the movements of the facial muscles in conjunction with each of the 6 basic emotions and explains variations. "Fear" can have at least 4 mouth positions and each one symbolises a slightly different type of anxiety or level of fear. Also interesting is the discussion of expression blends; such as Happy with disgust,anger,or surprise.
I remember seeing an advertisement a few years ago where someone was supposed to look really worried but in the closeup photo the actor just raised his eyebrows, the basic signal for surprise. The advertising company probably spent £100k on the campaign, based on facial expression, but didn't know the basic expressive signals, or see their error, they definitely should have read this book!
The Darren Brown-o-philes will be interested in Chapter 11 which explains "micro-expressions" which last less than a second but indicate the true nature of what the subject is feeling. These operate a bit like a blush, by the time you've felt it, its already happened.
If you are interested in portraiture, acting, makeup, or any kind of analysis of emotional states espressed on the face, it is a great reference book and one that is always cited in other face perception studies.