There's also Kindle competitors, like the Kobo. You can also bet that if this becomes a wide-spread concern, another e-ink reader may come to market that offers privacy and security, maybe some sort of open-source, secure-by-default, ereader. Some attempts at this have already been made [1], but its not clear how strong the market demand for that is and if it will be successful. If you really want a privacy-centered reading experience, the easiest way to do this is just borrow the printed book from your local library.

[1]: https://hackaday.io/project/168761-the-open-book-feather