Two classics I've read (or reread) in the last couple years --
The Catcher in the Rye
A Separate Peace
-- makes me wonder why anyone would want to read these without having been assigned to. Well, I guess I did, but it was only to find out why they are considered so important in literature. I didn't.
They say that people who enjoy Catcher in the Rye have an increased chance of becoming serial killers or assassins. Not a strong recommendation.