The question I get asked the most by aspiring writers is this, There are a million books about (mourning, weight loss, parenting, etc). I'm just a nobody. What can I bring that's any different?
My answer is always the same... you.
So What if you're not a celebrity? You have something that nobody else has: your story, your voice, and your life experience. Don't let anybody tell you any different.
Yes, there have been lots of books about losing a loved one. But there have been no books about losing your loved one.
That doesn't just apply to non-fiction. How many times have we read boy meets girl, or girl meets vampire? What sells books is your unique narrative voice. What do you have to say and how can you say it differently from everyone else?
As a writing exercise, my teacher had us all go outside and look at the road. Then he had us go inside and write a paragraph about the road. As you can imagine, the six of us, though we all looked at the same road, had remarkably different things to say about it. One of my favorites said it looked like a meeting place for lost souls.
Point is, you bring something to the table that is awesome and unique and deserves to be written. So don't try to make your book like any other that's been written before. Don't model it after a best seller.
Model it after you.
Tell your story.