Since ancient times, the heart has been associated with love and passion, but the familiar heart shape (♥) dates from the Middle Ages. Heart-shaped valentines are actually a special instance of the entwining of books and hearts that Eric Jager examined in The Book of the Heart.
When we published his book, Jager wrote a special feature for our website in which he traces the heart-as-book metaphor through history. Read his essay, “Reading the Book of the Heart from the Middle Ages to the Twenty-First Century.”