Eric Jager traces the history and psychology of the self-as-text concept from antiquity to the modern day. He focuses especially on the Middle Ages, when the metaphor of a "book of the heart" modeled on the manuscript codex attained its most vivid expressions in literature and art. For instance, medieval saints' legends tell of martyrs whose hearts recorded divine inscriptions; lyrics and romances feature lovers whose hearts are inscribed with their passion; paintings depict hearts as books; and medieval scribes even produced manuscript codices shaped like hearts.

"The Book of the Heart provides a fresh perspective on the influence of the book as artifact on our language and culture. Reading this book broadens our appreciation of the relationship between things and ideas."-Henry Petroski, author of The Book on the Bookshelf