It reflects badly on John Thorpe that, as Rachel G says, the only two novels he says he likes are the bawdy "Tom Jones" and the nasty (yes, I've read it, there's some really yucky stuff in there!) "The Monk".

However, I think that Catherine might not be able to pick up on that, since I am sure that she would have read neither of them -- not the sort of thing that a clergyman would allow into his house. Still, she might be aware of their scandalous reputation, even if she hadn't read them...