I think Louie's story is very interesting. And we learned a lot about what life was like for a lot of the POW's of the Japanese. We thought the German's were bad. The Japanese were a lot worse.
Louie was an honorable man in the face of what he went through. He did endure a lot of hardship, but he never gave up or gave in.
The religious aspect is not really all that much and it's not something that's in your face. It's a part of Louie's life. But there is nothing there to turn anyone off (IMHO).
For those who did not read this because you thought it wasn't literature, you are dead wrong. Literature is not about fancy words or prose. It's about telling the story in a way that grips the reader and keeps the reader reading more. It's telling the story so that you get a lot out of it. Unbroken definitely is literature. Some of the books that are called literature may have fancy writing and good prose, but if the story is not interesting, it's not really literature.