They can be about all: psychology, religion, phylosophy, history etc.
The last one that I read and found very interesting was : "The Art of Persuasion" by Robert B. Cialdini.
The author explains the psychological mechanisms of persuasion. Studies show that most of the tactics used by the specialists of persuasion fall into six basic categories: reciprocity, commitment and consistency, social proof, liking, authority and scarcity. To recognize them can be useful in every day life.

