The Great God Pan by Arthur Machen

So every so often I read a book that is so creepy that I don't really know why I read it in the first place. This was one of those. Arthur Machen was, according to Wikipedia, which knows All Things, a mystic as well as a writer, and this is a well-known novella of his published in 1890. The scene begins, as so much Victorian fiction does, with a scientist who is all arrogance and know-it-all-ness. He has raised a young woman on whom he performs an experiment designed to 'open the mind to all things.'  The scene in which he describes his 'right' to do this is appalling to a  modern reader. I wonder if it was to Victorian?  Either way, she comes out of her reverie both physically and mentally damaged. The rest of the story centers on the panic and pain that this experiment unleashed in to the world.

I can't write any more without some serious spoilers, so I'll stop, but let's just say it's all freaky and worth reading if you like things that make you lose sleep because a) wondering what the heck happened in this story and b) still being scared out of your bejeezus even though you never quite figure out (a).