Well, having just committed a Vast Sprawling Epic Labyrinthine Novel, my first (that's right, I am going to write a Huge Honking Novel every 50 years, at this rate), let me poke into what, if anything, I learned about the dark art of fiction.
First lesson: something has to happen. I bet I threw away 100 pages of lovely, lyrical passages, sinuously flowing, artfully crafted sentences rolling along like salty music, because nothing actually happened in those passages. Even I, their inky dad, had to sigh and blubber and cut them. If nothing is moving, if no one is leaping into the next moment or crashing into a tree or happily doing exactly the wrong thing at the right moment, then it's not a useful part of the moon mission. Huge lesson for me.
Second lesson: real characters do things that the author is horrified by. If the people in your book are real, then they are essentially in charge of the action. I had ideas for the plot, you bet, but quite often my ideas were trumped by what the characters were doing, and it seemed to me that often they were happily giving me and my plans the finger. I called a friend of mine, who is a superb novelist, to complain about this. "Let them go," he said. "Real people do real things." I suppose there are novelists who map out every twist and turn, graph and chart the action, and then write to fit, as it were, but, at the moment, I cannot imagine doing such a thing. There would be a carpenter's pleasure in writing a novel like that, snicking all the pieces cleanly into place, planing and polishing the result, and there, voila, a lovely piece of finished work — but, to me, a great deal of the pleasure of committing a novel was discovering with my fingers what was going to happen next. Quite often I would open the file in the morning, read through what I had written recently, and then type furiously to see who was doing what and why. We often say, as readers, that we want books to be page-turners, but I wonder how often writers themselves write to turn the page, so to speak.
Third lesson: readers swim and live in novels in ways they don't in nonfiction, or so it seems to me from the first wave of letters I am getting from readers. I love being an essayist (such a dignified and graceful title), and my heart has many times been pierced by the letters I get for my essays; but novels are whole worlds, and I am fascinated by the number of people who have already said they miss the world inside the book. Notes like that are almost enough to make me want to write another novel, God help us all.