Joseph Conrad's classic that was turned into a great movie, although mediocre version of this story.
In the story Marlow and his pals are sitting around on the deck of the cruising yawl Nellie, waiting for the tide to shift and the sun to go down. To pass the time Marlow decides to tell a story of the time he was a freshwater sailor and had to taken a steamer up a river in the Congo. He had gotten a position with an ivory trading company through the influence of an aunt and as his first job he was tasked with taking a station manager up the river to retrieve Kurtz.
Now Kurtz is a trader who has gone nuts with his own unlimited power over the natives. His followers are not willing to let him go and attack the steamer as it draws closer to the clearing where he has set up camp. Marlow and the station manager dock the boat and meet up with Kurtz, who, it turns out is quite sick and near death. He resents the fact that he is being called back. After all, he's gotten so much ivory for the Company that it's piled up at camp.
The end of the movie is not exactly the same as the book, so I'll stop here.
There is some really great writing here.