Gosling starts with a basic psych primer, explaining the five basic personality traits and how they can be identified. He slowly builds to a larger analysis of how things, actions, and appearance affect other people's views of you. Essentially, people sing their personalities everyday and you can figure it out - if you know where to look.
People who walk with their heads up and their arms open are considered by other people to be open. People who shuffle with their heads down are not. People who have a variety of unique items - books on different subjects, unique art - are considered open. People with a lot of books and a lot of art that are all on the same subject are not.
People who display pictures of their family may be buoyed by frequent glances at these favorite people OR they may be showing off their beautiful family - it all depends on where the pictures are placed. Pictures that can only be seen by the person at the desk are for their personal use. Pictures displayed outwards - towards the guest seats on the opposite side of the desk may indicate pride and the desire to show off.
People respond better in studies to other people who are considered concientious - neat, clean, organized - versus the people who appear narcissistic - every hair in place, expensive clothes, indication of intense up-keep (expensive highlights, makeup, etc).
A person may say they are organized, but only a look at the private areas of the house will tell the tale for sure. Superficially organized people - or people who are trying to impress - will only organize public areas - their desk, the common areas of their house, etc; whereas, truly organized people will not rest until every part of their living life is organized - both public and private.
If you are interested in finding out more about your friends/family/coworkers or you think you might want to be the next Sherlock Holmes, learning how to snoop effectively is key. Gosling's book is a reveletory look at how people's stuff says much more about them then they think it does.