I am a devoted Salinger reader ever since I fell in love with Holden Caulfield when I was 15. I learned later that Catcher in the Rye should be read at five or ten year intervals. The story changes remarkably as the reader ages an comes to see Holden in different lights. The quote about sentimentality is attributed to Seymour to R. H. Blyth. That’s probably accurate because Blyth was an influential Zen poet and essayist and Salinger took refuge in some form of Zen Buddhism after his traumatic experiences in WWII.
Re-reading an old favorite when you are older is an excellent way to understand the difference between reading a text and having an experience.