THIS is the real problem. Books (or music, movie, whatever) tied to one specific platform, without any chance to migrate somewhere else - somewhere where is more comfortable/convenient for you.
Libreture maintains a list of such bookstores [1].
> At the Publisher's request, this title is being sold without Digital Rights Management Software (DRM) applied.
Still, signing into public devices with your private credentials and data is a bad idea. What if they kick you out of the store or take away the device your were toying with before you manage to wipe/reset it?
Being tied to a specific platform is unacceptable.
Ownership of data should be included in service, but rarely is.