I was completely obsessed with the book and used to carry a copy with me everywhere. (no jokes)
Obviously I identified heavily with Holden as a teenager, as i got older (which is quite recently I'm only 18
) I was able to understand it from a more objective point of view. It's about growing up and wanting to remain a child, Holden loves children because they aren't "phony" they do and say whatever they feel. The reason the book resonates so deeply with teenagers is because they're all having to come to terms with becoming an adult and entering society with all it's pointless rules and responsibilities. The funny/sad thing is that you can see Holden struggling against doing all the phony things he hates so much yet unable to not do them (he still shakes hands and says "glad to have met you" to that guy in the bar, he doesn't accuse the guy of stealing his gloves when he did, he only wears his cap the wrong way round when no one is looking amongst some examples)
To be honest, I think I will always carry the same angst/existential crisis stuff that Holden displays, because that's the kind of person I am, but as an adult you sort of learn to forget about it and just "get on with stuff"
The funny thing is, and I think it's what the book is saying as well, is that this state of angst is somehow better or more "noble" than just forgetting about it? Like Holden, I hate the idea of just becoming another "phony", I hate the idea of losing this angst, even if it's a crappy feeling.
Hmmm... *re-reads post* maybe I am still a teenager
Anyway, agreed it's awsome on so many levels, it's funny as well, i love the scene with the taxi driver when he asks "where do the ducks go?"
You should read Salinger's other stuff, he's got a bunch of short stories with the same vibe to them as Catcher which are awesome