Good book, a bit slow, but that isn't bad perse, it just means there is a lot of explanation of the situation, historical background and deepening of its characters. The book not only teaches a lot about Dutch history and warfare in 1672, and about the way of living then, it also makes one interested.
As for the story, it does not really unfold. Only the characters unfold. One could say that it is a few years in the life of a young boy. However, the end is very abrupt and that is what saddened me about this story. It's a little like the book "The Lily Theater" by Lulu Wang. It's like a diary and doesn't really have a moral to the story. In fact, the book already explains in the beginning that it is memoire and as such it does not need to have a moral or even a storyline. Still, however, with such a profound deepening of the story one would think that something extreme, a climax or anti-climax, would happen.
On one hand I would recommend this to teenagers, but on the other hand, for Christians, I would not recommend this because it provides a very one-sided, be it true, version of how Christianity was practiced in those days. Surely, many people were practicing Christianity as a culture or tradition, without realizing the importance of it, but there are many Christians who are serious and devout. Most importantly, the author (perhaps unintentionally) makes it seem like Christianity is just that, while it is so much more.