It's important to understand that Holden isn't necessarily right about the world and it's phoniness, and Salinger didn't mean him to be. He wanted to show what it's like to be at that transitional age and the doubts most of us experience then. Holden is an extreme version of that. Holden is scared of becoming part of the "phony" adult world. What intelligent teen hasn't felt that at some point? But there's also some phoniness in him too, as there is in all of us. Yes, he's grieving his brother, but more importantly, he's grieving his loss, and ours, of a childhood innocence that we all go through. This is what makes the book so universal.