and I understand that you can use non-Kindle readers to read kindle books bought from Amazon, bit it’s a bit of faff.
Use Calibre a free bit of software to manage your libary which will read all formats and convert them to the right format for the device you have attached to the pc. It’s simple, free and completely does away with format issues. Brilliant.
One thing to note on the kindle is that they are pretty fragile, it takes very little to flex the unit and crack the screen, it happens with normal use, you don’t have to drop it or sit on it to break it. If I replace mine it’ll only be with the cheapest one or I may look at the Sony though I’ve no idea if it’s any more fit for purpose than the kindle.