It also discussed personal space, and how people tend to have their own boundaries as to how much personal space they would prefer to have. Some people don't need much personal space, while others like to have people they talk to at arm's length away, and depending on whether they were interested in their conversation partner or not, would allow that boundary to be crossed. I found this very interesting.
There was an experiment the authour suggested: at a party, find someone who clearly needed a lot of personal space. He went on to detail how to find them, and I forget what else. The authour then started explaining the game - which is to talk up this person, and keep getting closer to them. The person would probably back away. The object of the game? Keep doing this and see how far you can maneuver the person until they abruptly quit the conversation.
This used to be interesting to me. I never really went to a lot of parties, only dreamed about it, but it always sounded like something successful people did.
For some reason, recently I thought about this book again, because when I was younger (around 12 or 13), this informed a lot of my understanding of body language. And it wasn't all bad; plenty of it was useful observation and I could see how it played out in a lot of situations which involved a lot of people.
And when I remembered the game, I thought, wow, that's a horrible thing to do to another person.
For the first time it struck me how awful it is to single out a person based on their requirements for personal space, and then violating that personal space all for the sake of amusement or experimentation.
It really just shows how stuff that one finds really informative at some point in life can turn out looking so awful at another point in life.