I saw the movie first, and let me just say that I'd date any of these actors, though their characters weren't quite my type. They're greasers, which isn't all bad, but most of them seemed to feel stuck in that role, even if they didn't have to be. For instance, Darry (oldest brother, played by Patrick Swayze) was smart and could have made something of himself, if he didn't have to take care of his little brothers (Sodapop and Ponyboy). Ponyboy (the narrator) also had the potential to get out, but he seemed undecided about whether he wanted that until the end of the book.
But I'm getting ahead of myself.
It's a story of the greasers, and what happens when one night Johnny accidentally kills a soc in self-defense. Shocked, they run and hide out for a few days until their friend comes back to get them. They decide to turn themselves in, but before they can, they see a burning church with schoolchildren stuck inside! They rush to save the kids and Johnny is badly injured in the process. The greasers plan a climactic rumble to end all rumbles with the socs. They win the rumble, and shortly thereafter, Johnny dies.
I take it as a coming of age story. Ponyboy and Johnny have to decide what they want to do: get stuck in the role of a greaser like Dally (who meets with an unfortunate demise), or "stay gold", and not get mixed up in that trouble.
Interestingly, I just watched An Officer and a Gentleman, which was kind of the same story. Richard Gere is a loser, then he joins the navy (because he wants to fly a jet--this sounded absurd to me at first, but it turned out to not be a joke) and because of his dedication and his moral code, he ends up with a badge, a girl, and a really hot uniform.