>Funnily enough, it's possible to remove this DRM protection, but it's also not something completely legal, and makes me question why did I decide to legally buy the e-books in the first place.

Did you seriously stop yourself from saving your books, that you'd bought, from erasure by these shitty systems because of some silly DRM laws that are to begin with grossly unfair in this context?

Please, next time, strip that garbage and be done with it. Regardless of some silly regulations, consider it a basic assertion of concrete and very fair, paid-for ownership.

Or just pirate them.