A wonderful “crossover” book is a new history of the First Crusade by Jay Rubenstein called Armies of Heaven: The First Crusade and the Quest for the Apocalypse. This is a superb, utterly entertaining, thought-provoking, at times (rightly) disturbing, and thoroughly illuminating account of the First Crusade. It is written by an eminent historian, who has gone back to the primary sources and re-narrated the events of 1095 to 1099, when something on the order of 100,000 Christians marched across Europe, through Byzantium, Anatolia, and down to Palestine to retake the holy city of Jerusalem from Muslim control. Though eminently scholarly, it is pitched to a non-academic audience. Rubenstein tells a wonderful story and, although specialists will be able to identify his arguments and his engagement with historiographical disputes, his narrative is free of the kind of “inside-baseball” argumentation that can sometimes muddy the overall picture. This book conveys the excitement, anticipation, horror, and amazement at the extraordinary events that started one of the consequential phases of the history of the West and the history of the relationship between Christianity and Islam. Worth the read.