When I was a kid, I stumbled upon a book my mother had stored away in her closet. It was called, "Nineteen Ways to Read a Person," or something to that effect. I read it and became interested in the subject. I suspect my mother was interested in getting ahead in her business. I remember she once told me that she always wondered what life would have been like were it not for her having children. I suspect she would have founded a successful business and made lots of money. Instead, she chose to mix the two. It was a delicate balance to be sure. I have yet to see a woman match her incredible work ethic and ability to keep things together when everyone around her is completely nuts. But that book has always stayed with me.
I've read more books on the subject over the years and then studied sociology and social psychology in grad school. I read as much as I can on the subject of reading people, understanding people, relating to people, effectively listening to people, conflict resolution among people, etc... The one constant, if there is such a thing, is the fact that when conflict arises and emotions are running high, people make mistakes. They can either be seriously honest and use that honesty as ammunition for the fight or they can make things up based not on fact, but blind emotion and/or rage which can have its roots based under the jealousy tree. Younger people tend to do the latter.
It's important to know who it is that is reading you. He or she could watch you from a distance or he could be straight forward, confident, and in your face. He could be a con who talks as fast as he reads people. These are some of the most dangerous people that are in our society. However, their insincerity always gets these guys in the end.