The Crusades: An Encyclopedia surveys all aspects of the crusading movement from its origins in the 11th century to its decline in the 16th century. Unlike other works, which focus on the eastern Mediterranean region, this expansive four-volume encyclopedia also includes the struggle of Christendom against its enemies in Iberia, Eastern Europe, and the Baltic region, and also covers the military orders, crusades against fellow Christians, heretics, and more.

This work includes comprehensive entries on personalities such as Godfrey of Bouillon, who refused the title "King of Jerusalem," and St. Bernard of Clairvaux, who tore up his own clothing to make symbols of the cross for crusaders, as well as key events, countries, places, and themes that shed light on everything from the propaganda that inspired crusading warriors to the ways in which they fought. Special coverage of topics such as taxation, pilgrimage, warfare, chivalry, and religious orders give readers an appreciation of the multifaceted nature of these "holy wars."