Neil Gaiman's novel The Graveyard Book begins with all but one member of a family being murdered in their beds at night. Yet this is a middle grade novel! It makes me consider how Gaiman could pull off such a thing. What makes writing true horror, and what is just scary?
It's a long-established tenet of the movie industry that the amount of blood shown is one way to measure the maturity of the audience needed. In the Gaiman, that opening scene is bloodless. Of course, there must be blood, since three people are knifed to death, but it isn't described. The agony of their deaths is not described. Instead, the knife is described:
"The knife had a handle of polished black bone, and a blade finer and sharper than any razor. If it sliced you, you might not even know you had been cut, not immediately. The knife had done almost everything it was brought to that house to do, and both the blade and the handle were wet." (N. Gaiman. The Graveyard Book. New York: Harper, 2008, page 5)
Wet. Not bloody. It's the implication that's terrifying.