In the book The Boy in the Striped Pajamas Bruno is a young boy who is moved to the countryside with his father due to his father's new duty. His father is an important man to the Nazi military but Bruno just sees him as his father. Once he even argues with his father about the move being stupid. His innocence does not allow him to see how important a figure his father is at the place.
Bruno also sees the people in the work camp. He asks about them being in their pajamas and is told that is what they are wearing. He believes that they are getting to hang out all day. As a child, he can not imagine that his father would be involved n anything cruel nor can he fathom the idea of a concentration camp and especially a death chamber.
When Bruno is told by Schmuel that he has been separated from his mother and siblings but lives in a dorm with his father, Bruno can not understand why that would make the boy sad.
The father is a man torn between his mother's disregard for his career, his wife's horror at the position he is employed in, and his family's inability to adjust to the changes. In the end the real tragedy comes when Bruno sneaks into the camp to help his friend and ends up in the chamber being killed.
Bruno remains a true innocent even as he is being put to death. He has been trying to find his friends father. They get shoved into a dark room where they hold hands until the end.
The whole story makes us sympathize with the child in the camp, Bruno's innocence and life uselessly lost. His father and mother's pain at the loss of the child. The reader's own pain as both children prepare to die as innocents.
The story has been written so that the reader continues to feel sad long after the book is closed.
The boy in the striped Pyjamas is an eventful book - with things that, in a normal perspective, would be quite gruesome. John Boyne uses the perspective/the eyes of a child to portray innocence.
-Bruno is Naive. He doesn't understand what is happening on the other side of the fence. He thinks that the children in the concentration camp are more fortunate than he is, he believes they are having fun, when really, they are trapped.
-The innocence in Shmuel & Brunos friendship. They love each other, they are friends, despite the circumstances of inequality.
Sympathy is given to those on the other side of the camp. For example, we learn about Pavel. We learn that he had spent many years practicing as a doctor, then because he is a Jew, his status is reduced to a waiter.
Many forms of sympathy are shown throughout the Novel, mainly given throughout the main characters.
Hope this helped in any way possible. :)