Damn near impossible to find DRM free books to purchase though.
My method has always been to buy physical books (which is also better to support the author, because they get a bigger % of the price you pay.
And then, there are other creative ways to download the ebook... (without buying from Amazon, or other monopolists.)
https://www.reddit.com/r/Calibre/comments/1q1uza4/successful...
If publishers/authors want my money, they can release a version without DRM.
Calibre web and calibre web automated downloader remove a fair bit of the clunk.
Ironically, files downloaded from "other" sources have no issue. So they're just making it harder to buy from Amazon legally.