So many people have written reviews, that I feel kind of silly adding my 2 cents. The last time I read Heart of Darkness was when I was an undergraduate in college, so it's been some decades now. My daughter's reading it in her high school AP Literature class, and I thought, why not revisit it? It's very interesting to see how my impressions differ from those of my earlier days.
Having tried my hand at writing several novels, I'm blown away by the sophistication of Conrad's book. My writing, which is very much "genre fiction" tends to be pretty much plot-focused. I also feel like most communication these digital days is also plot-focused, in that the reader is asking: "What's the point?" "What's the bottom-line?" "Don't waste time" -- Just like writing this review, you're probably wondering - OK, what's the point?
The point is -- Conrad's book has the complexity of a piece by Beethoven or Rachmaninoff, something dense, slow to digest - whereas my stuff is "Chopsticks" - and a lot of books these days (due probably in part to the constraints put on writers by the publishing industry to write "sellable" books) are written for quick consumption and written fast, so the writers can earn their livings...
Another thing that stood out for me in reading the book in the current cultural context is how much Conrad (or is it merely Marlow's POV?) criticizes Imperialism and racism (despite the historically dated use of his own racist language). He's pretty damning about "whiteness" - in his own particular way. When I was in college, our class spent a lot of time on the symbolism of good/evil, but I don't remember discussing this aspect of the book.
Finanly, in my earlier reading of the book, I didn't notice how all of Kurtz's alleged "greatness of ideas" (that so impressed Marlow) are never actually uttered in the book - leaving a haunting absence - except for those famous words: "The horror, the horror."