Why has the novel been so widely read for so long in Westen culture? What is the primary source of its appeal?Is it aesthetic, emotional,...

The answer above is a great one and really speaks to the
importance of the content of this novella and its expression of one of the central
elements of the human experience: our understanding of good and
evil.

To this, I would also add that Heart of
Darknessis an expertly crafted example of the artistry of literature. The
themes, imagery, and symbolism are all tightly wound and all contribute to the central
theme and idea presented in this work. This novella is exemplar of literary 'high
art.'

Also, the novella stimulates an emotional response in
almost everyone who reads it. Conrad himself often criticized his lack of a central
message or moral to this story, but believed the reading experience of this novel could
have a profound and sometimes transformational impact upon the
reader.

For all of these reasons, Heart of
Darkness appeals to readers and remains a key title in our literary
canon.