Found this in a book box, was pretty sure I hadn't read it, I was right.
Rightfully declared a masterpiece, and while looking at online criticisms (most invalid and centred around the colonizers interpreting their culture and influence in currently unacceptable ways) it is only that inasmuch as these readers clearly didn't understand Marlow's point of view.
It's influence on literature - well; of course the movie "Apocalypse Now", but as well Blaise Cendrar's "Moravagine" and Celine's "Journey to the End of the Night"; In "Alien" wherein the crew is set out upon a corporate mission whose architects have concealed the peril; there are more I'm sure and it reads like more than a couple of my family vacations.
Anyways; it appears he as he was remarkably prescient; the same year he published it the Vounet-Chanoine expedition was under way; and if you've not heard of it maybe review the wiki of it here.
Every bit of it terrifying, and every bit as uncomfortable, only this was - relatively recent - history.