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.
My wife wrote a book and brought copies to sell. Someone asked her if she brought ones to sell and my wife said yes. Later when we meet with her she’s like “you’re sure I can have this?” My wife says something like “yeah I brought enough” and then she never paid lol. Even worse, the next day she wasn’t randomly holding a $20 bill and put it away. Either she’s the most rude and insanely conniving person ever or our life was a sitcom because wtf. There’s more context but I don’t wanna yap too long. My wife almost even took the money out of her hand thinking she just didn’t have cash the night before.
All that said, you deserve to get paid for your work!