One day in college I was trawling the library for a good book to read ... I could get through only a tiny chunk ... That chunk changed my reading life forever. The author argued that you didn't truly own a book (spiritually, intellectually) until you had marked it up.

Old-school marginalia was a kind of slow-motion, long-form Twitter, or a status-less, meaning-soaked Facebook, or an analog, object-based G-chat.

It's probably natural ... to worry that ... serious reading will become impossible. Yet books are curious objects: their strength is to be both intensely private and intensely social — and marginalia is a natural bridge... serving equally well as a bridge between online and literary culture.... a point of contact that could improve both without hurting either?