Is Kurtz important as a character in himself or because of his effect on Marlow? (up to the beginning of Book 2)
I though of analysing in what way Kurtz helps us to understand more about Marlow in order to answer the question but i lack of ideas and examples to support the thesis ....
Many thanks from France
You've asked if Kurtz is important as a character up to the beginning of Ch. 2. By that point, the reader should be cognizant of the fact that we still have not met Kurtz and that the primary focus is on Marlow. Kurtz is supposed to be an eloquent, intelligent man; Marlow distrusts words and is a believer that doing, (specifically work) is what makes a man. Marlow turns to "work" again and again, for example, at the central station when he must dive into repairing the boat in order to avoid becoming completely frustrated over the inefficiency, disorder and exploitation going on around him. Yes, Kurtz gives Marlow a purpose (he must bring him out of the jungle), but up to the point you mention Kurtz serves to develop the theme of Marlow's journey of self-discovery and to help the reader learn more about Marlow. Overall, this is Marlow's story.
Kurtz is important as a character because he is central to the plot. In Chapters One and Two, you hear a lot about Kurtz but yet Marlow has not yet met him in person. This builds up a sense of mystery and helps drive the plot along. The reader soon becomes as interested in Kurtz as Marlow is.
For examples, the brick-maker mentions Kurtz and the Manager as well. Marlow overhears the leader of the Eldorado Expedition (the Manager's Uncle) and the Manager talking about Kurtz. Also, Marlow runs into the Russian who is totally enamored by his meeting Kurtz and repeats over and over again, "He enlarged my mind". All of these 'rumours' about Kurtz help develop the plot. There are other examples - I marked a book up once with tags at every time Kurtz is mentioned by someone before we ever met him.
That would be my argument that he is important as a character. Of course Kurtz is vital to Marlow because he serves as an example of Marlow's internal journey and the danger Marlow himself could find himself in, in the heart of darkness. However, I think you could argue Kurtz as being important just based on his role of building up mystery and suspense in the story.