There are several messages of John Boyne’s novel The Boy in the Striped Pajamas. An important one is that, despite their differences, there are similarities between people. Another important message is that in an oppressive society, horrible things can happen to anyone, and so it is important for rational people to fight against tyranny.
The similarities of people, their differences notwithstanding, can be seen with the two boys, Bruno and Shmuel. When they first meet, the image the author presents is of two boys of about the same height and same age sitting cross-legged across from one another. They seem almost like two bookends facing one another, separated by a fence. Moreover, the boys discover that they share the same birthday and are both nine years old. Bruno says,
“I'm surprised, that's all. Because my birthday is April the fifteenth too. And was born in nineteen thirty-four. We were born on the same day.”
Shmuel thought about this. “So you're nine too,” he said.
“Yes. Isn't that strange?”
“Very strange,” said Shmuel. [...]
“We're like twins,” said Bruno.
“A little bit,” agreed Shmuel.
Of course, they are not like twins. The symbolism of the fence represents a very real difference between them. Shmuel is a prisoner, while Bruno is free to roam wherever he wants. However, by showing the two boys this way, the author is conveying how alike they are fundamentally. They find much in common and much to talk about even though they are different in many ways.
The other important message is of the unpredictability inherent in an oppressive and inhuman society. This message is also epitomized with the use of the fence and can be seen when Bruno crawls under it to help Shmuel. Bruno is caught up in the Nazis herding the Jews into the crematoria and, like Shmuel, Bruno is killed. This underscores how terrible things can happen to anyone in this kind of dictatorial regime. In this message, Boyne conveys that people need to fight against tyranny.