Well, as elsewhere, the most important thing is the right approach to a marketing strategy and the right work with data. After that, the correct optimization of all content and data to improve promotion. After that, launch automation of all actions and go on sales and promotion of your book. If this is interesting, then you can read the article on how to properly do google optimization https://www.owox.com/blog/use-cases/google-optimize-tutorial/. In any case, you need to know!