Behavioural economics is usually the most popular genre of economics book. That's probably because it's one of the more human parts of economics, and, on the face of it, the least spreadsheety (that’s almost certainly not true). Basically, it's the psychology behind how people make decisions. For that reason it's popular in business and marketing, as well as politics. Which means it might be useful to read up on as a defence against businesses and marketers (not nice bookshop business, though. We would never psychology people).
When we were researching all this we found people mentioning Adam Smith (1723-1790) as discussing some principles of behavioural economics. So it's been around for a while, but unless you are particularly hard core, we wouldn't recommend starting with the 18th century.