Here's an interesting piece by Simcha Fisher, Dangerous Books for Teenage Girls. She's talking about books that are not bad in themselves, but may feed unhealthy tendencies in the mind of a teenage girl. Interestingly, she names Walker Percy's novels as an example from her own youth. I can see the point: Dr. Thomas More's lusts, for instance, are very significant as theological ideas, but they are certainly treated pretty lightly morally, and a naive reader can get the wrong idea.
Anyway, this started me to thinking about books that were similarly dangerous to me. One that comes to mind is--no surprise here, I expect--The Catcher in the Rye. I think it was considered a somewhat immoral book at the time. If nothing else, its extensive profanity made it unacceptable in the eyes of many parents and educators. But there wasn't much harm for me in that--all my friends cussed like sailors, and so did I. The harm lay in its encouragement of my already-present alienation, self-absorption, and self-pity. Worse, it suggested that the reason I was so unhappy was that I was better than everyone else, perhaps even that my unhappiness was itself a sign of superiority. Not a good message for a 15-year-old.
I don't know that all the science fiction I read in my teens did me much good, as it mostly assumed a more or less atheistic and materialistic philosophy, sometimes explicitly. Arthur C. Clarke's short story "The Star" definitely disturbed my imagination; I think I half-believed it might really have happened (there's a synopsis here). On the other hand, sci-fi fed my sense of wonder and my love of the mysterious, so it was certainly not all bad.
Although I was barely still a teenager when I read it, as I was in at least my second year of college, Blake's Marriage of Heaven and Hell was very definitely an unhealthy influence. With this, though, I may be getting out of the category of good books which may have bad effects and into books which are simply bad. "Those who restrain desire do so because theirs is weak enough to be restrained"--what a nasty bit of poison that is for an adolescent male.
Among the worst of all was not a book but a movie, Zorba the Greek. It was very popular among artsy-bohemian people when I was in college: "a celebration of life" and all that. I saw it two or three times. There is a scene where the earthy vital spontaneous life-affirming Zorba tells the more timid city fellow that (quoting from memory) "God is merciful and forgives many things. But there is one thing he does not forgive. And that is if a woman calls a man to her bed, and he does not go" (emphasis as I recall it from the movie). I might have been just as well off to stick a needle full of heroin into my arm as to have those words embedded in my consciousness, which is what happened. It's not so much that I did or didn't follow this counsel (sorry, no confessions forthcoming) as that it gave me an entirely wrong idea of what a man ought to be, what I ought to be, what sex ought to be--as if sex wasn't already a big enough problem. It's bad enough to fail in following one's ideals, but you're really in trouble when the ideals themselves are wrong.