This is a history book. Stark delves into the crusades, starting with the Muslim conquest of the Middle East, the North of Africa and Spain, stopped by the Battle of Tours/Poitiers in 732, all the way to the last crusade and the fall of Accre. His conclusions are quite interesting and for all I can see, thoroughly documented:
The Crusades were not unprovoked. They were not the first round of European colonialism. They were not conducted for land, loot, or converts. The crusaders were not barbarians who victimized the cultivated Muslims. They sincerely believed that they served in God’s battalions.
Very much worth reading for anyone with an interest in history.

And it was nice to read something else than theology, for a change