Here is a short passage from what I wrote today in Writing the Entertaining Story.
Chapter 10: The Reader’s 50%
What you bring to the story.
As a writer, it is your job to bring a basic structure to your world. You must tell the reader what it your character is, and explain the challenges your character faces. You must make the character seem real and the setting in environment seem real by having the character interact with the environment. Occasional sharp-focus details will lend credibility to both the protagonist and world building.
What is not your responsibility is to fill in all the blanks. That’s not your job. That’s the reader’s job. And when the reader fills in the parts of the canvas that you’ve painted that’s called The Reader’s 50%.
What the reader brings to the story.
A reader brings to any story the sum total of their life experiences. When you describe a high school, the reader automatically thinks of their high school experience. It’s inevitable, it’s expected, and really in a lot of ways that works in your favor. All you have to do is a writer is point out the things that might be different from the general experience of most people going to high school.
When you describe a sailing ship on the ocean, if that person has ever been sailing all their experiences on a sailboat will come to mind when you bring up a sailboat in your story. While it’s important to describe that briefly, but accurately, for those who have never been sailing… for those who have been sailing mostly all you have to do is evoke their memories, without making any mistakes that would throw them out of the story.
Readers bring an enormous number of experiences to what they read: literally, a lifetime of experiences. And this is a good thing. You can tap into that wellspring of experiences when you write. These experiences are much more vivid than anything you could ever scratch out with a pen or type into a document. So when you’re grounding a scene by mentioning the smell of wood smoke at a campfire, for many readers you will tap into their visceral memory of sitting around a campfire themselves at some point in their lives.
This is why too much detail can be a problem in your story. If the details don’t match up with your readers experience, you cannot evoke the readers experience. It’s also why people often complain that they don’t like the movie because doesn’t match the book. What the movie doesn’t match is the reader’s 50% — the part that they brought to the table when they read the book.