His research and teaching focus on religion, violence, nostalgia, and apocalypse (in various combinations), whether manifested in the Middle Ages or modern world. This includes events and ideas such as the Crusades, the so-called “Terrors of the Year 1000,” and medieval religious and political life more generally. He also has presented and published on modern medievalism, such as recent white supremacist appropriations of the Middle Ages and pop culture phenomena like Game of Thrones or video games.

He has published several books and numerous articles. He also has presented at dozens of national and international conferences and has given talks at Harvard, Princeton, Georgetown, the University of California-Berkeley, the University of Wisconsin-Madison, the University of Virginia, the University of Minnesota, the University of Tennessee-Knoxville, the University of Kent, and Nottingham Trent University. In 2010, he was a visiting researcher at Westfälische Wilhelms Üniversität-Münster, and from 2016-19 he was an elected Councilor of the Medieval Academy of America.

His public writing has appeared in such places as The Washington Post, Time, Forbes, and The Daily Beast. Interviews with him have aired locally, nationally, and internationally. He is currently a columnist for Smithsonian Magazine.

His new book, with David M. Perry, is out now: The Bright Ages: A New History of Medieval Europe (HarperBooks, 2021).