In The Boy in The Striped Pajamas, Bruno is the narrator and the plot unwinds from Bruno's perception although the reader can understand the implications of those things beyond Bruno's scope.
John Boyne develops Bruno's character through Bruno's experiences, relationships and the way in which he faces and deals with matters beyond his understanding, as if they are just new opportunities, to be taken at face value. He does not understand how important his father must be as one of "The Fury's" top commanders. As a very accepting child, Bruno, although inquisitive and ready with questions, is a very obedient child who never reads further into a situation beyond what he is told.
The author reveals Bruno as an innocent, respectful child, oblivious to class differences or the purported reasons for them. Even outside the safety of his home in Berlin, Bruno's character develops as an average, self-absorbed nine-year old's character would, ensuring that his character is believable and realistic. His attempts to appear to grasp adult concepts add an irony that adds to the deep loss the reader feels by the end of this book:
"We can chalk it up to experience,' he added, a phrase he had learned recently and was determined to use as often as possible."
Most nine year olds do not question the authority of others but do see the world from a very selfish perspective: "I think Father should think twice about his job, don't you?" he asks Maria, aware only of the unfairness towards himself.
Bruno does not wonder why some have jobs as maids and butlers and others as high-ranking army officers; why some children's fathers' are greengrocers and others are soldiers. He knows "all the jobs that ... decent, respectable fathers" do and it is enough for him.
In stark contrast to his own character development, the reader is introduced to Schmuel who has a completely different perception which does not detract from Bruno's in any way. Boyne allows the boys' similarities to bring them together as friends and not their differences. Just as Bruno envisions life as he has seen it through the window in Berlin, then from his new home, so Schmuel's outlook contrasts sharply as he "didn't like to look out of it (the window) because then I would see the wall and I hated the wall."It is beyond Bruno's comprehension that his father, or anyone, could purposefully harm and destroy the lives of others for no reason so he cannot process the possibility.
Even at the end, as Bruno and his "friend for life" face the gas chamber together, after Bruno has realised that there are not families picnicking inside the fence and it is strikingly different than he imagined and even though he wants to go home, his character remains pure and he has no comprehension of his imminent fate.