When I was maybe 11 my mother introduced me to Agatha Christie. I think it was Mom's thinking was that nothing much happens in an Agatha Christie book that you wouldn't want a kid to read. Well okay there are those dead bodies, but even they are done with good taste, artfully arranged and already dead so you don't even have the violence factor.
Christie's most famous character was the Belgian detective Hercule Poirot, a rather comic figure with a mustache obsession. But very very people smart. He understood that people do fall into types or categories and usually act according to type. Yeah, I know its terribly un-PC, but these books were written back before WWII, most of them.
Another of her characters was Miss Jane Marple. Miss Marple was an elderly spinster lady (it was the 1930s, people; they had spinsters back then) who lived most of her life in one small English village of St. Mary Mead. Miss Marple has learned in her life time that what most people call intuition is really just being guided by your own life experiences. In her first appearance in "The Murder At The Vicarage" Miss Marple describes it this way: "Intuition is like reading a word without having to spell it out. A child can't do that because it has so little experience. But a grown up person knows the word because he's seen it often before." I've always thought that was an excellent analogy. You recognize when something is a bad idea without having it "spelled out" because you've seen this situation before, or heard about it, or heard of someone else's experiences. Recognizing those similarities gives Miss Marple an advantage over the police quite frequently.
Miss Marple also says, in many ways through out many stories, that people are really very much the same wherever you go. And I've discovered over and over again how very true that is. People do fall into 'types'. Oh, not obvious ones. But if you live long enough, and you pay enough attention, you start noticing things. That perfectly likeable person that turns out to be completely unreliable. The grouchy complainer that actually comes through for you before anyone else. The clean cut kid at the store who ends up short changing the next customer. And somehow your 'intuition' recognizes pieces of them in other people you meet.
This was Christie's genius. The plots were fun and the mysteries clever. But what made her books timeless is the characters. Those bits and pieces of real life behavior that she weaves into fictional people. Not just the good and bad people, but the everyday people. The person who means well but ends up pushing someone away. The one who wants so badly to be impressive that they make entirely the wrong impression. There are variations on themes but essentially people fall into a finite number of categories. And often when we are reading we'll come across some character, over the top and more of a caricature, perhaps; but all the same, they remind us of someone. Because art really does imitate life. And everybody really is very much like everybody else.