If you go onto Amazon and under the category of "Shop Instant Video" you type Horror; many Horror films come up. I clinked on purchase to find out what people had been buying.
The top film is "What We Do In The Shadows". This movie is a vampire movie. As "Knock Knock" will be a paranormal; the fact that the top movie isn't means that there is space for my movie. However i know that paranormal is still interesting to the audience because movies like "Ouija" are popular.