On first read, I found The Turn... to be a fascinating story: Is the narrator/governess seeing ghosts? (Truman Capote said yes.) Or has she merely gone mad? (As Edmund Wilson argued.)
(Here's an essay from The New Yorker that gets into this: http://www.newyorker.com/online/blogs/books/2012/10/ever-scarier-on-the-turn-of-the-screw.html)
I'd like to tell you that upon digging so deeply into the text, I have a conclusive answer for you, but the truth is that the deeper one digs, the more layered and obscure the narrative becomes. It's no wonder that literarians have been debating this for more than 100 years.
However, if pressed, I would tell you that I do believe the governess saw a ghost or two, AND that her fear at what was very possibly benign, grew to the point of insanity. So yes to ghosts AND yes to crazy.
But that's just my opinion. What's yours?
The Turn of the Screw: http://www.gutenberg.org/files/209/209-h/209-h.htm