I'm not going to bother with the Amazon affiliate links anymore for the books. No one has ever bought anything through the site and I encourage people to use their libraries anyway so if you want an image of a particular title I've reviewed, you'll have to find it yourself.
I mentioned last month how I've become enamored with Derren Brown. Well, I thought I would read some stuff on body language to see what I could learn. I read Janine Driver's You Say More Than You Think and Allan Pease's The Definitive Book of Body Language and watched a DVD called Secrets of Body Language. I also thumbed through Joe Navarro's What Every Body is Saying, which my son recommended as he read it a year or two ago, but it seemed to be the same content as the other materials. None of them were of much use. Pease's book and the DVD spent a good deal of time using retroactive looks at celebrities and politicians and pointing out poses/stances/actions that potentially indicated one thing or another.
Potentially is the key word here. You really have to have an understanding of an individual's "baseline" before you read anything into their body language. If you know someone regularly does A and then they do B, you probably know they're mad/lying/want to have sex with you/whatever. But if you don't know what A is and you try to interpret B, well good luck. Is that person fidgeting because they are lying or because they are nervous or because they downed a few Red Bulls? Who knows? The folks behind these materials seemed to think they know. Amazingly, with hindsight and body language analysis, they were able to tell that Richard Nixon was often times lying. Astounding.
Driver's book had the benefit of being a seven day program to learn about body language. There were exercises at the end of each chapter, several of which required a camera to videotape yourself so you could see how you look to others. Not exactly convenient. But the exercises promote observational skills which are always a good thing.
I didn't find either book to be useful and therefore am not recommending either.