"So what?", you say. "Lots of people read books but few become writers and even fewer become famous writers." Fame isn't my goal, just a really good book. A book that at least one person can say "I couldn't put it down!" Just one and I'll be happy.
Really good books have two key elements: a story and a theme. The story is what you read. It's the protagonist, the hero, facing and resolving some sort of conflict and being forever changed. The detective finding the killer. The ugly duckling finding true beauty, etc. The theme is more subtle. It's the hidden message if you will. Good triumphs evil (or not), free will vs control, the search for happiness, etc. Though it may be hidden, it is nonetheless pervasive and does as much to drive the story as the action itself. I have a theme, now I need a story. That's where I'm at.
I don't know, though I'm learning, how other writers approach the task. Do they have a story first? A character they like and want to do something with or to? Or maybe it's an exotic locale that sparks it all.
So, I have a theme. Which means I have something to say, yes? But why a novel? Because when it comes to grand themes , just giving you my opinion isn't going to be very interesting. Everyone has an opinion. Maybe, just maybe, if I can wend and wind the theme through an engaging story I will have made you think, made you ponder things you might not have ever pondered before or better yet helped you answer a question that's been bugging you, consciously or not. Regardless of whether you accept or reject my side of the story, I will have helped you escape for a while and just maybe charged some dusty synapses along the way. I'll have achieved my goal.