The largest commercial provider of ebooks, audiobooks, and other digital content such as streaming videos in the world, a 2023 report estimated its market share as perhaps being upwards of 90%.
This company notably powers the Libby app for borrowing books.
The headquarters is located in Cleveland, Ohio, United States.
Are there any European alternatives available?
That’s a good tip, although around my way it’s standard to need to visit a local library at least once in order to finalise sign-up (in the UK it’s standard to need to show photo ID when signing up, and libraries won’t generally bother setting up a way to do that remotely).
I know one person who happily collects library memberships every time they’re in a new area with a bit of time on their hands though. They’ve got a very impressive wallet-full of library cards!