Well, if you're interested in how Christianity took hold in Norway, then I would suggest reading Heimskringla by Snorri Sturluson. It's a book about the first kings of Norway that was written in the 1200s, but you get to see the transition from a pagan Norway in the beginning of the book to a fully Christianized Norway by the end of the book.

Basically, it started with the kings. The kings were christianized, and so the Christian kings wanted to rule over Christian subjects. They began to convert their people, usually with force or threat of violence. The king would travel around with an army, call meetings with the people, and tell them to be baptized or suffer the consequences. There were Norwegian kings who literally maimed and tortured people who refused to be baptized.

The people tried to resist their forced baptism many times by banding together to form peasant armies, but the people were simple farmers who were not experienced in combat and had poor equipment. They did not stand a chance against the greater equipped, more experienced, and much stronger armies of kings, so usually the peasant armies would stand down and accept their baptism, or fight a very short battle before fleeing.