There are a few reasons why ebook sales have been declining over the past four years. They doubled in price, when publishers gained control over pricing, instead of Amazon or Kobo charging their own. You cannot loan an ebook to a friend and cannot resell an ebook, once you have finished it. Lots of people have embraced Overdrive, and are borrowing ebooks from the public library. In 2018 65 different library systems each loaned out more than one million ebooks in the space of a year; one system, Harris County Public Library in Texas, loaned out more than two million ebooks.
— Read on goodereader.com/blog/e-book-news/our-love-affair-with-ebooks-is-over