At what age group is Stevenson's Dr. Jekyll and Mr. Hyde aimed?

While Stevenson is noted for writing
children's adventures like and , the
novel  is categorized as an adult horror novel. The striking thing about
the origins of this story is that it was inspired by a nightmare from which Stevenson awoke
screaming. The dream was of a villainous monstrous transformation induced by a white powder. One
can only speculate that his fear resulting from the dream convinced him that adults were the
proper target for such a frightening horror tale about the consequences of rejecting the need
for controls on the powers of evil.

The most significant textual evidence
that this is a story for adults is that much of the story revolves around a philosophical
discussion of the nature of good and evil as in Jekyll's letter:

it chanced that the direction of my scientific studies, which led wholly toward the
mystic and the transcendental, re-acted and shed a strong light on this consciousness of the
perennial war among my members. ..., I thus drew steadily nearer to that truth, [...] It was on
the moral side, ... that I learned to recognise the thorough and primitive duality of man; ...
the two natures that contended in the field of my consciousness, ... I was radically both; ...,
I had learned to dwell with pleasure, ... on the thought of the separation of these
elements.

The internal debates within the text regarding
the nature of good and evil are of an esoteric nature and not composed for the consideration of
any but an adult mind. Another textual proof that it is a story for adults is that there are no
youthful heroes or heroines: the characters of interest are exclusively adults, like the
intended audience.