@JohnPhilpin Kindle books are still on Amazon. There may be third party software (Calibre?) that would let me download to a computer and strip DRM and manage my ebook collections, but I very rarely read a fiction book twice so I don't bother.
I have ebooks on 4 services:
I started out with ebooks on Palm Pilot PDM buying ebooks on Fictionwise. (I loved Fictionwise.) Then Barnes & Noble bought Fictionwise but let me transfer my library from Fictionwise to Barnes & Noble. So I have lots of books there.
Amazon Kindle. Lots of books.
I'm sure I have a couple of books with Apple, because I tried them out.