This is not an anti-Kindle rant. I have purchased (rented?) several Kindle titles myself.
However, YSK that you are only licensing access to the book from Amazon, you don’t own it like a physical book.
There have been cases where Amazon deletes a title from all devices. (Ironically, one version of “1984” was one such title).
https://www.nytimes.com/2009/07/18/technology/companies/18amazon.html
There have also been cases where a customer violated Amazon’s terms of service and lost access to all of their Kindle e-books. Amazon has all the power in this relationship. They can and do change the rules on us lowly peasants from time to time.
Here are the terms of use:
https://www.amazon.com/gp/help/customer/display.html?nodeId=201014950
Note, there are indeed ways to download your books and import them into something like Calibre (and remove the DRM from the books). If you do some web searches (and/or search YouTube) you can probably figure it out.
For Kindle specific ripping, I think it changed a year back and now you need to have a kindle connected before the Amazon servers poop out some magic unlock key/the whole book. After that you’re golden, but during the rip you need a kindle device…
https://www.thewindowsclub.com/remove-ebook-drm-with-calibre#:~:text=If you’re using Kindle e-ink devices%2C connect Kindle,DeDRM plugin and click the Customize plugin button.
They explain the Kindle difference when using Calibre DeDRM tool in this article.