I typically don't know what my novels are about until I've written most of them. That probably sounds utterly back to front, so I should clarify a little. I know what it's about in general terms. I know the shape of the plot. I know roughly who the characters are and what they're doing. I just don't really know what it's all about until I've written something.
I'm talking about theme here. Theme or issues, or whatever you want to call it. Message, maybe, although that's probably putting it a bit strongly, since you can bring up points on a theme without having a defined message to convey. You can ask questions without providing answers. Indeed, there's a case for saying that's the more interesting thing to do.
But it's often hard to be clear about your themes in the first draft. You can take the same story and make it about a dozen different things through the way you tell it. The things you choose to concentrate on. I've got this vaguely Arthurian idea knocking about at the moment, and have had for a while now, except I can't decide which way to go with it.
With the ones where I've made an effort with theme, which means novels like Court of Dreams or the Glass, it's only come to me quite late in the piece. That moment where I've sat down and thought 'okay, I have a novel, but there's nothing much to it. It's just not coming together right'.
Working out what it's about seems to work like a kind of glue for the story. Or maybe a way of seeing what works and what doesn't. Because it can help you to be ruthless with your story. To cut out bits that aren't relevant, not because they're not good (we wouldn't have written it if we didn't think it was good) but because they don't quite fit with the rest of it.
So what about you? Have you ever written something, looked back through it and only then realised what it was really about?