“Because fiction requires a mighty engine to thrust it ahead—and take the reader along for the ride—backstory if used incorrectly, can stall a story. A novel with too little backstory can be thin and is likely to be confusing. By the same token, a novel with too much backstory can lack suspense. […] Remember this: The fantasy world of your story will loom larger in your imagination than it will on the page.
Balance is the notion that every element in the story exists in its proper proportion. […] When you lavish a person, place, or object with descriptive details, readers expect them to have a corresponding importance.” Between the Lines: master the subtle elements of fiction writing, by Jessica Page Morrell