Imagine having a cloud of user-contributed commentary, maps, photos, audio and video annotating the paper books you hold in your hand. Think that's something you might enjoy? I think I would. Check out the video below.
One question I do have is this: why use QR codes? Couldn't software recognize the unique combination of words on the page and load a URL based on that? Perhaps it's about namespaces and particular communities of content online. This way you could pick a particular edition of a marked-up book you want to participate in.
The codes on the page do feel like an aesthetic flaw, but perhaps we'd grow used to them. The net benefit of living, social books certainly seems compelling.
Presumably it will only be a matter of time until a whole lot of newspapers, magazines and other printed content is refreshed with cloud-based dynamic and social content accessible by mobile phone.