I'd argue that we never really "owned" books. Put aside the mundane physical object and assume that a book is a work of culture, authored by somebody else. What can "own" possibly mean in this context? You don't somehow commandeer its copyright by gaining an indefinite right to consult it. The words "own" and "buy" and "sell" are fundamentally ill-suited to abstract quantities such as knowledge and information and ideas. Perhaps our attachment to this (IMO) egregious category error of "ownership" can be explained by centuries of capitalism and (more recently) consumerism.

> What can "own" possibly mean in this context?

This sounds unnecessarily reductive. By "own" I would mean that I can re-read the book again and again and again as many times as I want as long as I take good care of the book and prevent it from disintegrating.

But the DRM e-books can't be used like that. That was their point.