I have bought a few kindle books, but don't have a kindle. My goal was to have any electronic format I can print by my own and ring bind it. I love ring bindings, it allows for better page turning.
So far, I converted every book by reading it online in a browser and took a screen copy of every page. Then I took a screen copy of every page and joined them into a pdf.
I think this method works well for sheet music, but I would not do it for regular books. All the convenience of digital reading, like text-search is lost then. Or changing the font-size.