Before you publish your book you should hire an editor to catch your mistakes, polish your pages, make sure you have followed the rules of the genre, and to keep your thesis (main point) from meandering all the way to China and back. An editor is an extra set of eyes looking at your manuscript but with distance. This is important because the more familiar you, or someone close to you, are to the story, the less you will see. Your mind automatically inserts information into the text that isn’t really there; your eyes will “see” words and phrases and ideas that are not really on the page. A fresh set of eyes will catch this.
An editor will check for several points of interest but one of the top reasons a manuscript does not succeed is thesis control; too many ideas all wrapped into one story. This often happens when a writer is so excited about telling a story or has multiple ideas that he tries to cram everything into one book. A recent book I edited had this problem. The author is well entrenched in his career; he has been in his line of work for over 20 years. He was involved in a catastrophe that shook him to his core. He decided to write about what happened. Nothing wrong with that, but he left the tracks when he decided to put ten different topics into the book! Granted, he did not sit down and purposely set out to write a book that would end up all over the map. But in the end, the book was not focused and will ultimately fail because the purpose is not clear.
How does a book get off track? By not following strict guidelines during the writing process. The writer needs to be diligent about why he is writing in the first place and then stick to the original plan. For example, if you are writing about a father who takes the life of his child and wife, then information about how brain function develops in children probably doesn’t fit. This is way off topic.
There are a few ways you can test yourself to decide if your thesis is out of control. Ask yourself some questions: Who is the main character and what is his journey? Am I telling only his story or am I telling three other people’s story as well? Am I telling stories because they are interesting or because they are directly related to my topic?
If you stick to your thesis, your point, your topic, or whatever you want to call it, your book will be much more likely to see substantial results. And your reader will thank you.