If I had a plot that was all set in advance, why would I want go through the agony of writing the novel? A novel is a kind of exploration and discovery, for me at any rate.
I think the hardest part of writing is revising. And by that I mean the following: A novelist has to create the piece of marble and then chip away to find the figure in it.
I don't work on my Sabbath. I write five-and-a-half or six days a week.
A non-fiction writer pretty much has the shape of the figure in front of him or her and goes about refining it. A work of non-fiction is not as difficult to write as a work of fiction, but it's not as satisfying in the end.