When you write your book, make sure you know how you’re writing for and stick with it. I recently read a psychology book where the author stated in the introduction that he originally planned the book for professionals but it was so useful that they toned down the language so that it could be for either lay people or professionals. I think that was a bad decision.
The early language that introduced the idea was appropriate to both groups. Neither group had a lot of information about what he was speaking about unless they already knew his technique and philosophy.
The next section was written simply, more for lay people with some added notes that would be appropriate for professionals. As a lay person, the notes were annoying but not bad. As a professional, I might have been tempted to skip the book because of the simplistic way this was written.
In the final section he promised to talk about how to help each of these categories of people. This is where it clearly became about the professional. He took one of his categories and wrote a long and specific treatment plan based on all the expanded knowledge he had on this particular constellation of problems. After writing several more chapters going more in-depth with the same category of person, he then talks about ways you can generalize for all the other categories. This is fine for a practitioner, but for the lay person who might have been hoping for some personal insight, this was a let down.
Both categories of readers were ultimately let down by the book. Understand that no matter what you write, it’s not for everyone. It targets an audience. This author, who thought his ideas would be appropriate for lay people and professionals was right. However, the idea that one book would work for both was not. He’d have done better to write two books. One for lay people and one for professionals.
The most important thing you can do as a professional writing a book based on your knowledge is to target your audience. Stop worrying about the people who don’t fit that category. You, or someone else, will write the book for them.