Yes, you can backup your Amazon ebooks. Here are some ways you can do it:
-You can use Amazon’s Kindle Cloud Reader application to backup your books. With this method, you can download your books to your computer, which you can then backup.
-You can also use a third-party application, such as Calibre, to backup your books. Calibre can connect to your Amazon account and download your books automatically.
For more information, you can check out this article:
https://www.howtogeek.com/howto/4667/back-up-your-amazon-kindle-books-for-safe-keeping/