Have you ever looked at a really old book? I mean something at least 200 years old. Aside from the occasionall work like Don Quixote, they’re nearly always some treatise on religion or some academic endeavor. Where are the trashy romance novels from the 1500s? I’m sure the predominant thinking is that there was a lot more censorship back then, but I think maybe that kind of material was just so well used that it hasn’t survived to the present day. Think about the books you read often. Aren’t they in worse shape than your old college textbooks? Which are more likely to survive for centuries? Suppose some disease wipes out humanity, and several centuries later extraterrestrials visit our world. They’re going to think we all read Dialectal Readings on Metaphysics instead of Harry Potter. They’ll wonder how we got wiped out if we were so smart.