Towards the end of the book, Bradbury has one of the "book covers" be Schopenhauer. He is among such people as Mark Twain and Jonathan Swift.
What this implies about Schopenhauer is that he is "dangerous" like these other men. The other men here were pretty cynical and were also pretty rebellious. Neither of these is a trait that the society in this book would like.
Specifically, Arthur Schopenhauer was a pretty pessimistic thinker. He concluded that people could never have what they want and that they should try to get rid of their desires. This also goes against what this society thought.