So, I read The Outsiders, even though I didn't wish to do so. (Amazing what I'll do for school, sometimes). I read it for the first time when I was 11-12ish, and thought it was OK then. Difference was, then, in the late 1970's, there wasn't much in the way of YA books to choose from, so as books went, it was pretty good, then anyway. Now, at 39, I was able to see it through the lens of 28 years more life experience, and have to wonder if it really resonates with today's YA anymore than it did for me back when.
Thematically, the story holds up even all these years later, possibly because it's a story as old as time. It's about looking beyond the labels and actually seeing the real person. It's about understanding that we're all more alike than we are different. It's about realizing that every single one of us is fighting our own battles every single day. It's about knowing that there are unknown depths of strength in everyone. It's about accepting that things are not magically better on the other side of the fence.
I don't know if too many teens would read it for fun, though. In one of the local schools, it's read in an English class; this alone almost automatically takes it out of the running for a for-fun good book.