I think you've missed the point somewhat. I don't think Poe is a scary writer, nor do I think Stevenson is and I credit this to the fact that we aren't scared of things which people living a couple hundred years ago were.
I think if you read Jekyll and Hyde with the expectations of a twenty first century reader you'll get barely anything from it. The ending for one is pretty poor when you level it with other science type novels. However, when you put it into context it's frightful and controversial and a fantastic little read. This goes for many classics, very few in my opinion manage to succeed as great novels in their time, and then as great novels in modern time without allowing for context.
It's as Ben Mines says, "What's wrong with Treasure Island? If you allow that it's an adventure book for Victorian schoolboys, it's perfectly readable."
Same goes here.
x