Have written two automotive books that sold successfully--and one that didn't! First, write about something you know. Second is to write about a topic that you can conveniently research. And write a book that fills a need, even if it's just a niche, a book that will be unique. A successful book must also have an audience broad enough to make it a financial success for the publisher.
In fact, you should find a publisher before you get deeply into the project. A good publisher can help you with research access, advances, guidance, scope, writing style, editing standards, publicity, and more. Of course, he will first want a thorough outline, perhaps even a sample chapter. Your writing experience, even if it's only for a club publication, helps interest a publisher.
Hope this helps.
Frank