Desmond Morris has written a few... They're academic but accessible. can't think of titles so you'll have to search his name on Amazon...

a book called everyday mind reading goes in depth about body language and non-verbal cues. But the studies where poorly thought out, their research was laughably organized, and they had alot of fruedian theory in it, so most of their conclusions are probably wrong. still, it might be a good a place as any to start (i don't recomend it though)