It is not nearly so lurid nor horrific as the title might lead one to believe. It’s really just an Edwardian ghost story.
The comparison I kept coming to is a wholesome, English take on J K Huysmans Le-Bas, which I now want to read again. A young man who is vulnerable to the deductions of occultism, but ultimately rejects it after going nearly as far as one can, and returns to his faith in the end. Benson was an Anglican minister who converted and became a Catholic priest and Huysmans a writer within the French Decadent movement who had a Pauline moment and became a devout churchgoer and eventually an oblate.