He is the author of nine books, including the companion volumes Renewing Christianity: A History of Church Reform from Day One to Vatican II and The General Councils, along with 101 Questions and Answers on Popes and the Papacy and Church History 101. He also created and edited the Paulist Press series, Rediscovering Vatican II, and is a frequent media commentator on church history and contemporary Catholicism. The Archbishop Gerety Fund for Ecclesiastical History was established by the Most Reverend Peter Leo Gerety, Archbishop Emeritus of Newark, to advance studies in ecclesiastical history, especially the history of the Roman Catholic Church in the United States. Among its various activities, the Fund sponsors lectures each year at Immaculate Conception Seminary School of Theology.