This document discusses connecting digital bookshelves through open standards like OPDS (Open Publication Distribution System). OPDS allows people to find, acquire, and read books from any source or device using different ebook apps. An OPDS bookshelf can act as a global shelf, backing up files, automatically adding books to social networks, and providing a consolidated experience across retailers and apps. A bookshelf is essentially an API that can integrate features like annotations, highlights, and social interactions to enable distributed reading.