The Crusades Trilogy is a series of historical novels written by Swedish author and journalist Jan Guillou about the Consolidation of Sweden and the Crusades. The main character of the trilogy is Arn Magnusson, a fictional Knight Templar in the 12th century, who becomes a witness as well as a catalyst to many important historical events both in his homeland of Västra Götaland and in the Crusader states.
https://en.wikipedia.org/wiki/Crusades_trilogy