The companion guide to the video series Christianity and Islam with Dr. Timothy George recommends the following books on the Crusades:

Belloc, Hillaire. The Crusades: The World’s Debate . Tan Books, Rockford, Ill., 1992.

Maier, Christoph T. Preaching the Crusades: Mendicant Friars and the Cross in the Thirteenth Century , Cambridge University Press, 1994.

Runciman, Steve. The First Crusade (abridged), Cambridge University Press, 1980. Orignially volume one of The History of the Crusades, 1951.