The language is extremely dense—late James in all his rococo rhetorical finery—and though the book runs only some hundred pages, it casts a spell not merely shadowy but extensive: it feels longer than it is.
If you haven't read Henry James' The Turn of the Screw , read it now. First published in 1898, it's free on Project Gutenberg; it's the ultimate ghost story.
That said, my all-time favorite ghost story is M.R. James' Casting the Runes.
"James" is the surname of both writers. Coincidence? (Cue Twilight Zone theme)...