I'm reading "Non-things: Upheaval in the Lifeworld" by Byung-Chul Han, who has things to say about it. "Things" are naturally possessions to be owned; the non-things that we as a society are moving towards are information to be consumed. If you have a physical book, you can pass it along to someone else, margin notes and dogears and all, but the experience of an e-book is fundamentally different. You might feel like you 'own' the bits because they're on your local computer and have no DRM, but your relationship to the actual item is not one of ownership. Just think about leaving your favorite book as .epub to someone in your will to see how non-sensical that would be.