Photo by National Gallery of Art, Washington, D.C.

ON THE COVER: The angel Gabriel, sumptuously robed and jeweled, smiles knowingly in this detail from “The Annunciation,” by Flemish artist Jan van Eyck. Art historian Jane Dillenberger takes us on a journey of the mind in “Dual Impressions—Looking for Style and Content in Christian Art,” letting us see van Eyck’s painting and another “Annunciation,” by Sandro Botticelli, from different perspectives.