I first read Robert Cialdini's book Influence: The Science of Persuasion when I was in graduate school studying judgment and decision making. I was amazed not only by the power of the psychological levers for influence that the author describes, but how easy he makes them to understand. It turns out that MANY things guiding my every day decisions have their roots in psychology, but what's really amazing and a little distressing is how these levers are used deliberately by people in the know to influence me. Free samples at the super market? They're given out because the reciprocity effect makes you more likely to buy the product. Fraternity hazing? The consistency principle makes you put up with it. Buying things on sale when you don’t need them? It’s the scarcity principal and loss aversion making you do it.
What's equally impressive about Influence is how effectively Cialdini communicates these ideas. He provides one of the best examples I've ever seen of straddling the line between practical examples anyone can recognize and how it relates to academic research published in scientific journals. Each chapter focuses on one major concept and then dives deep into it before ending with a set of recommendations about how we can guard against unwanted influences. The latter often boil down to "You just gotta be aware of it," but sometimes they offer pointed advice that can be quite useful.
For anyone interested in the topic of psychology and how it relates to what you buy, what you like, who you support, how you act, what you value, and what you think in every day situations, you can't do much better than this book. It’s a great combination of empirical science made accessible (and relevant) to the masses.