Gladwell's purpose is to make his readers aware of how intuition affects their experience of the world.
He describes the way that a thin slice of information can be used to deduce deeper insights. Psychologist John Gottman can predict with astonishing accuracy whether a couple will stay together or not just by watching them interact for a few minutes. The limited data points that he gathers from this interaction allows him to understand the couple's relationship on a deeper level.
Unlike Gottman's well researched system, however, many of us develop an intuition about things that we cannot logically explain. Gladwell offers the example of a tennis coach who could predict whether a player would double fault. He had no idea what tipped him off to his conclusion. He would just have a hunch, and it was almost always right.
Gladwell does not merely advocate for following our guts, however. He cautions that intuition can lead to making bad decisions, such as the choice to elect President Harding based on his appearance rather than his credentials. Prejudice is another area where following one's intuition can lead to making the wrong call about someone's character.
Gladwell follows this with several more chapters describing the errors in judgment that result in following our intuition or mind-reading. In his conclusion, he advocates for slowing down our thinking and understanding how easy it is for our subconscious to be influenced by factors of which we are unaware. He urges readers to retrain their subconscious in order to make snap decisions that are accurate.