Original short story by Joseph Conrad available...
...from Project Gutemberg.
If you haven't read it, you missed a lot from the movie.
Download it for free at http://www.gutenberg.org/etext/2305.
This movie has been one of my all-time favorites, and have watched it a dozen times. I owned it in VHS and when the DVD came out I got it. However, it was not until I read Conrad's story that I really got to understand many of the fine points.
Enjoy the reading!