What is the overall message that Salinger wanted the reader to take away from The Catcher in the Rye?
There are quite a few, overall meanings you can take from The Catcher in the Rye. One is that the structure of society is contrived and that many of the roles and rituals one must play and go through have become empty: simply a means of achieving successful positions. Holden is more than just a sarcastic kid. He's very intelligent and he can spot phonies when he sees them. He questions authority figures, not just for the sake of rebellion, but because he sees hypocrisy and a lack of authenticity and honesty.
Holden finds fault with Ward Stradlater for conforming to the typical All-American role for the macho male. This role, among others, is something Holden thinks is a facade, something only 'played' as a means to get somewhere in life.
At the end of the novel, Holden goes to Mr. Antolini in order to avoid his parents. Despite some encouraging words, Holden's suspicion of authority figures is again confirmed when he wakes up to find Mr. Antolini stroking his hair.
Holden wants to be a catcher in the rye to save people from throwing themselves over a cliff. Perhaps he wants to warn people, especially young people, about the phoniness of the socially constructed roles you must play in order to have success. He also wants to save people from becoming hypocrites, a trait he sees in almost every adult. And success for Holden is not social standing; it is living an authentic life.
Holden searches for authentic people throughout the book. Near the end of the novel, he considers essentially removing himself from society, the only way to escape living with “phonies.” In Chapter 25, he thinks,
“I figured I could get a job at a filling station somewhere, putting gas and oil in people's cars. I didn't care what kind of job it is, though. Just so people didn't know me and I didn't know anybody. I thought what I'd do was, I'd pretend I was one of those deaf-mutes. That way I wouldn't have to have any goddamn stupid useless conversations with anybody.”
For Holden, hypocrisy and phoniness are the inauthentic paths everyone must face, and try to avoid, when moving from adolescence into adulthood.