I believe that the most important book in the world is The Psychopath Code . The book is written by someome without any credentials in social science, but nonetheless, I believe that what it describes is true.
The core thesis of the book is that there are two competing strategies in humans. The majority strategy is what might be called altruism. Altruistic humans try to form long lasting relationships with each other that are mutually beneficial. This typically involves a certain amount of screening with increasing trust as the relationships progresses.
The other type of relationship that people engage in is predatory. The author uses the term “psychopath”, not in the medical sense, but in the colloquial sense. Psychopaths attempt to psychologically dominate altruists in order to take their resources.
One of the key reasons the author believes that psychopaths (he lumps in a bunch of different diagnoses like bpd, narcissists, etc.) are predators rather than damaged people is how well adjusted they are. They don’t generally suffer psychological damage from their own behavior (e.g. depression). That is generally reserved for their victims.