The main character, Bruno, who is 9 years old, does seem to be a lot younger in many of his thought processes. He may be a little simple, or the writer may have had difficulty remembering how a 9 year old really thinks ... or he was so protected from the real world by his mother that he was extremely naive. He lived in his own world, and he was the centre of his universe. It is touching how he pronounces things wrong: he calls the Fuhrer the "Fury", and he calls Auschwitz "Out-With".
Bruno's father is a Commandant in the Nazi party. He tells Bruno that the people in Auschwitz are "not people at all". Bruno is too young to understand racism. But his mother is depressed and (although she seems to like her husband's status) she doesn't agree with what he's doing. Bruno's grandmother is the only person that Bruno has seen stand up to his father, and openly oppose the views of the Nazi party. Bruno, though, doesn't understand what the argument is over. Through the dialogue that Bruno hears, the reader draws this conclusion. Bruno's mother says "we don't have the luxury of thinking", and she means that if they think any differently from the Nazi party that their lives are in danger.
At the end, Bruno's father seems to realise the horror of what he has done, even if only to his own son. He seems to realise the suffering that he subjected people too, even if he thought of the Jews as less than human. There is a reference at the very end of the book to Bruno's father being taken away submissively by other soldiers. I think this is the allies coming to free to Jews from Auschwitz and taking Bruno's father prisoner. He goes willingly because he thinks he deserves to be punished.
Such a simple, touching story. Everyone should read this.