I once worked for a startup where we attempted this, in a sense. We built an app that let users take a picture of their bookshelf, we scanned the spines then di

I once worked for a startup where we attempted this, in a sense. We built an app that let users take a picture of their bookshelf, we scanned the spines then digitized your "Shelfie". Our pitch was that we would give you the ebook of the print book that you own either for free or at a deep discount. We built a pretty complex recommendations engine on top of this and quite frankly, it worked really well. Simplified, if you have actual photos of bookshelves it's easy to start building recommendations. Person a read a,b,c, person b also read a,b,c, however, person a read e,f so maybe person b would also like e and f. The main issue is that publishers are archaic and building a sustainable revenue model against that is a challenge.