“Scary monsters are like hula hoops,” says John Malkovich. “They come in and out of fashion.” All the rage right now are monsters from the Middle Ages. “Book of Beasts”—an exhibition born of the bestiary, those Medieval books that mate zoology with fantasy—explores over 100 incarnations (manuscript, tapestry, sculpture) of these symbolic creatures. The ever-popular Unicorn, for instance, is associated with Christ and the Passion. —J.V.