The same thing happened to The Great Gatsby. On my first reading, I was so wrapped up in yellow cars and green lights that I couldn't hear the sultry energy of the prose or see it's cinematic sweep until a second and third read. I'm sure that Salinger would be better, or at least more memorable, a second time around as well.
This train of thought was prompted by the fact that Salinger has been in the news lately. It seems like our great literature is suffering the threat of the sequel (from a guy who goes by the name John David California, no less) in much the same way that our great films are. Maybe, instead of fretting over the possibility of a literary version of Grease II, we should revisit and reread the originals. They must be great for a reason, right?