Arts and Culture: An Introduction to the Humanities, co-authored with Robert DiYanni, Pearson/Prentice Hall, Upper Saddle River, NJ, two volumes and combined single volume, fourth edition, 2012 (vol. I, 540 pages, 294 illustrations; vol. II, 498 pages, 289 illustrations; combined vol., 670 pages, 537 illustrations); Chinese translation, 2011; Chinese translation, fourth edition, Tsinghua University Press, forthcoming; fifth edition forthcoming 2021.
Handbook for the Humanities, co-authored with Robert DiYanni, Pearson, Upper Saddle River, NJ, 2014 (450 pages, 443 illustrations, published in paperback and also as an e-book), Chinese translations, 2016, 2019.
Materials, Methods, and Masterpieces of Medieval Art, Praeger Series on the Middle Ages, Praeger Publishers Imprint Publication, Greenwood Publishing Group, ABC-CLIO, Santa Barbara, CA, 2009 (306 pages, 73 illustrations, published in hard cover and as an e-book).
Medieval Mischief: Wit and Humour in the Art of the Middle Ages, The History Press (Sutton Publishing Ltd.), Thrupp, Gloucestershire, 2004 (176 pages, 165 illustrations).
Art of the Middle Ages, World of Art series, Thames & Hudson Ltd., London and New York, 2002 (320 pages, 250 illustrations).
Holy Terrors: Gargoyles on Medieval Buildings, Abbeville Press, New York, 1997, fifth printing; French edition, Saintes Terreurs: les gargouilles dans l'architecture médiévale, Éditions Abbeville, Paris, 1997, second edition, 2000 (140 pages, 108 illustrations).
Medieval Monsters: Dragons and Fantastic Creatures, exhibition catalog, Katonah Museum of Art, Katonah, NY, 1995 (39 pages, 94 illustrations).
The Medieval Menagerie: Animals in the Art of the Middle Ages, Abbeville Press, New York, 1992 (Book of the Month Club selection); French edition, Bestiaire Médiéval: les animaux dans l'art du moyen age, Éditions Abbeville, Paris, 1992 (191 pages, 151 illustrations).