“The most important things to remember about backstory are that (a) everyone has a history and (b) most of it isn’t very interesting. Stick to the parts that are, and don’t get carried away with the rest.”
Stephen King
Imagine a reader in the middle of your book. They’re invested in the characters and the plot line you’ve created, they’re excited to see what’s next, and then, you, the writer, introduce a new character. The reader is excited to see how the story keeps flowing with this new character, but then, instead of continuing to push the story forward, you stop the action of the book to tell your reader the background of the new character, where they lived before, what they like or dislike, and how they feel about things.
Don’t you think your reader would be annoyed? Wouldn’t it be possible that by the time your reader got past the paragraph or two of backstory and back to the action of the story, that they could have almost forgotten what was even happening before the interruption?
This is the most obvious way to drop backstory into a book, and it’s also one of the most annoying to a reader. But there are smaller ways where writers often do the same thing. Sometimes, in a writer’s search to be as detailed as possible, they put in smaller backstory details that don’t matter to the current story.
Say your MC is a teenager who just got his license, and he finally opens the door to his new car for the very first time. What would a reader be expecting next? How the seats feel? If it have a new car smell? Whether or not he crashes it on his very first drive?
Those are the details that I would be interested in as a reader.
What if instead he puts his hand on the handle and then the narrator kicks in to tell us that this used to be his grandma’s car before she died, and it’s purple because his grandma liked that color, and his grandma bought it with money she got from a lottery ticket?
Is that an interesting backstory with interesting details? Absolutely. But here is the real point: you aren’t writing the grandmother’s story. So do these details actually relate to your MC? Does the origin of the car give him motivation to drive it well or drive it poorly? Does the seat get stuck when he tries to adjust it because his grandma was a foot shorter than him and then he has to drive hunched up?
It’s these questions that put us on the right track for using backstory. See, backstory is important when it enhances the story that the writer is already telling. If you, as the writer, give me all those details about the grandma but then don’t tell me how it changes the current story that you are telling, if you don’t tell me what changes in the story because of what has happened before, then those details become unnecessary. They become just one more thing for the reader to remember, and there will never be a payoff for them remembering them because they are never used in the story again.
So be very selective about the backstory that you allow into your writing. This will ensure that your readers are invested in the story you actually want to tell.