This isn't a problem, as inside Mastering Book Publishing, Stefan teaches you how to find profitable, high-demand niches on Amazon that you can publish a book on. You'll be guided through a step-by-step research process, and then learn Stefan's criteria for choosing the best one.
Mastering Book Publishing also teaches you how to hire a ghostwriter to write a book for you, if you decide you don't want to write a book yourself. There are many ghostwriters that are knowledgable on the topics you'd want to write a book on, as well as can do in-depth research to help ensure you publish a quality book.