I just read 'The catcher in the rye' what makes it diffrent to other books?

I know it mentions death. life. peace. betrayal. love. anger. Hate. I know and understand the book i just can't get my head around it like I've read it but somethings missing :/ There's something about it i'm just not understanding... why has is it seen as such clic book? and how has Holden's journey moved so many people? I feel like i'm missing the main plot nd i'm desperate to understand it... how did you feel after you'd read it?