If you write a series of non-fiction books on the same general topic, you can't help becoming a bit of an expert. The simple act of researching for your book will uncover more facts than most of your readers ever imagined existing. Why not put all that new knowledge into a use that can bring you even more revenue streams? Millions of people are seeking information online on every topic available, and they're signing up for online classes in droves. If you know enough about a popular topic to write a book about it, you certainly know enough to create an online class on the same subject. Sites such as Udemy allow you to create video classes and will host them and advertise them along with all the others on their site. For a percentage of your class fees, they make teaching courses a one-time effort designed for long-term revenue streams. 
Planning Your Course
Teaching a class is such a different experience than writing a book you might feel overwhelmed at the prospect, but you'll use the same information for both creations. Much like outlining your book, you'll need to plan out your online class before you begin to create it.
- Decide in detail exactly what you want to teach
- Craft the course goals. What should your students know be the end of the course? What information should they have?
- Break down your topic into bite-sized lessons
- Figure out your teaching style and decide how you want to use it to your best advantage
- Create quizzes, puzzles, discussion questions and other activities for your students
Producing Your Course
The easiest way for complete beginners to create an online course is to take Udemy's free course on the subject. It covers topics from production and course quality to choosing your equipment and getting on camera. It's a self-scheduled course, so it gives you an idea of what Udemy's courses should look like before you create your own. The best idea is to take the course all the way through, then view it again, doing the actions in each step along with the instructor. Udemy has advisors and instructors online constantly, plus social media groups dedicated to helping new instructors with any problems they might have. Once you have a finished product, you'll find advice on creating an enticing landing page that encourages viewers to sign up for your class.
Promoting Your Class
Use every marketing outlet you have to promote your course. You may have to market it for a few months, but it should eventually begin to gather word of mouth. If you have an email list, offer readers discounts for signing up for your class. When creating your landing page, allow short free previews for some of your sections. Create or use an existing YouTube channel to offer the first lesson free, and post a link to the rest of the class below. Post short snippets of class on Facebook, or link to them on other social media sites. You can even add details about your courses and links to the landing page in the back of any new books on the topic you publish. Market your class like you would any new book. You'll be reaching an entirely new audience, and may convert some of the video watchers into new book buyers.
Keep the Faith and May the Force be with You!
