Future of Books is Social
I just stumbled across Book: A Futurist's Manifesto by O'Reilly Media readable completely on the web. In What I Would Like in a Corporate Library, I talked about the library facilitating connections between people who share an interest in a book or topic. The way this book is published enables that, but most importantly there are a number of essays included that delve deeper into the idea.
What I think is important in social reading is to always give the reader the option of being social or easily "going dark." Sometimes people just want a bit of privacy, whether because they are reading about a sensitive topic, or just for a bit of piece and quiet.