1. You have to know how to write for them
You wouldn’t write a detailed technical manual using dense metaphors (unless you’re John Ashbery), and you wouldn’t write a hard boiled detective novel as if it were the King James Bible.
When it comes to tone, style, structure, and subject matter, your audience will have some basic expectations that need to be met before you can surprise them.
Who is your audience? Do you know how to write for them? Make sure you do plenty of reading within your genre before embarking on a large writing project. Then be sure to get feedback as you go, and enlist the help of an experienced editor as you near the finish line.
This is super-important.