I always wondered about ISBNs in books. I just came to know it costs more than 100 USDs. It may have been a good solution to pin point a book in analog ages. But, With digital services, I think we can do better.<p>So, I think a website, where self-pubishing authors can register their book, which provides an unique identifier for the book will be awesome. Technically, it'll be feasible to give this service for free, since, this site won't have daily returning visitors, and publisher market is comparatively low in number. But, providing the service for free might encourage spammers. I think any amount upto 5 USDs should be still reasonable for a digital unique identifier for a book.<p>A profile for the book, will be maintained online in exchange for the money, the profile will have cover picture, author, current version, publisher etc.