"Influence: The Psychology of Persuasion" by Robert Cialdini
The world is full of people whom Robert Cialdini call "compliance practitioners" -- people who make it their business to get other people to do what the practitioners want those others to do. They include salespeople, lawyers, politicians, advertisers, teachers, and many others. In the process of trying to obtain compliance, these people have all kinds of psychological tools at their disposal. Like any set of tools, the tools of compliance (or influence) are themselves neutral -- neither good nor bad in and of themselves, but equally of use to people with good and bad intentions. Thus, in a just and reasonable world, the "compliance practitioners" on the side of good should know all of the tools and when to appropriately use them, and the rest of us should be aware when those tools are being used on us -- so that we can decide when and when not to be influenced. "Influence" is a great dive into this important area of practical psychology, and it is just as readable as any non-fiction work you'll ever find.
Verdict: "Influence" comes with the highest possible recommendation. It is more practically valuable, important, and succinct than an entire introductory-level course in psychology.