Mortimer Adler, one of my learning heroes, says that one should annotate a book – have a conversation with the author, write summaries in the margins or at the head or foot of the page. Adler should know, he is one of the most well-read people of the 20th century, having written a two volume syntopicon of some 100+ topics gleaned from a 50+ volume encyclopedia. He even wrote books on how to read a book, and how to learn.