https://standardebooks.org/ebooks/bram-stoker/dracula
Another free book, check your local public domain laws to verify. Enjoy!
"Dracula is one of the most famous horror novels, responsible not just for introducing the eponymous Count Dracula, but for laying the foundations for many of the common tropes we see in modern horror fiction."
If you are thinking of reading some classics but you think they might not really hold up to your expectations, READ this one. It's absolutely timeless and it's amazing to me how actually scary the story is.
By contrast, skip Dr. Jekyll and Mr. Hyde. Oh no! Someone is walking in the neighborhood that doesn't appear to be a gentleman! Shocking!