A student asked, “I always like to write long prologues that give the history and culture of my story worlds, and set the stage for each novel. Is this bad?”
Short answer: even a little is often too much.
It is almost always best to leave out the history/backstory of any novel, especially in prologues. This doesn’t mean you shouldn’t know or even write the history of your world. The more you know what came before, the more real it will feel to your reader. But much of this is not meant for the reader. It is a kind of writing exercise that will help you tell your story with more color, more depth.
Your reader mustn’t be overwhelmed with stuff he has to know in order to enjoy the story. In fact, he doesn’t want to know a bunch of stuff. He’d actually prefer to have questions.
Here’s how it works: you should only tell your reader things after he asks you about them. Always make him ask first. How will he ask? This is what makes writing difficult. You have to learn how to drop hints and create questions in your reader’s mind—questions he will grow curious about. As his curiosity mounts, he will start to become intrigued and demand (internally) that you provide answers. When that happens, you can give him those answers and he will thank you. But if you give him the answers before he asks the questions, he simply won’t care, or, worse, he’ll stop reading.
It is almost always best to plunk your reader down smack in the middle of a conflict that creates immediate tension and presents an immediate unresolved question. Prologues usually fail to do this, and therefore usually weaken a story.