So what's the best, most open, e-reader to get?

I'm being pushed out of one increasingly locked-down corporate ebook racket and I don't want to sign up to another one.

So:

- Who's making the best e-readers that'll allow me to buy ebooks from different providers?
- Who's selling eBooks that aren't locked down to a single brand of device?

(I'm in the UK)

#bookstodon