Too some extent the book business model is similar to the video one. By commoditizing the publishing industry (free self publish with high margin) they generated an explosion of new authors on their kindle platform. However, their book business model is more advanced than the video as it cover both business model the service and the complimentary business model. This is reflected by the existence of the prime and kindle unlimited offer. Ultimately, it is possible that the video and possibly gaming business will evolve to something similar to the book business. This is a decade long strategic play by amazon, it won't happen overnight.