If sources were to be believed, he had a very complicated life. He was chased out of his country and denied his right to the throne, became a slave in Esthonia, was later reunited with a family member and had a fairly comfortable life at the court of King Valdemar, had many adventures as a Viking, and became a persistent and often harsh advocate of Christianity during his rule as the king of Norway. He was also a brilliant boy. He learned things much easier than his peers and he excelled in almost everything, like the heroes of various myths. Like every great hero however, he also had a weakness. He had a short temper and sometimes he was too trusting. Those qualities contributed to his downfall.
Leighton provided a short introduction which stated that he tried as much as possible to include accounts from trustworthy sources. It has twenty-two chapters and is told in a chronological manner with a few commentaries in some parts. I think it's well-written except for the parts where the author provided spoilers. He was able to provide a good characterization, although not consistently, instead of just narrating what Olaf does in some of the scenes.
I recommend this to anyone who is interested in reading history or biography, and even mythology and legends. I enjoyed this book but the spoilers sort of ruined it. I'm giving this a 9 out of 10 rating.