Featured libraries include the papal collections of the Vatican Apostolic Library, Trinity College Library, home to the Book of Kells and Book of Durrow, and the holdings of the Laurentian Library in Florence, the private library of the powerful House of Medici, designed by Michelangelo. With meticulous descriptions accompanying each featured library, we learn not only of the libraries’ astonishing holdings—from which highlights are illustrated—but also of their often lively, turbulent, or controversial pasts.