There are many examples of irony in this novel.
1. Both boys, Bruno and Shmuel, were born on the same day, and they died on the same day. They were both born on April 15, 1934 (pg 109) , and they both died in the gas chamber together.
2. Bruno says,
"It's so unfair...I don't see why I have to be stuck over here on this side of the fence where there's no one to talk to and no one to play with, and you get to have dozens of friends and are probably playing for hours every day." (pg 111)
What is ironic about this statement is that Shmuel is the one who is a prisoner, not Bruno. Bruno is free to do anything he wants. Shmuel is the one who is "stuck" on his side of the fence.
3. When Bruno tells Gretel too much about Shmuel, he pretends that Shmuel is an imaginary friend. Bruno asks her if she has an imaginary friend. She says,
"No.....I'm thirteen years old, for heaven's sake! I can't afford to act like a child even if you can." (pg 159)
The ironic part is that after saying this, she goes into her room and Bruno can hear her talking to her dolls and scolding them for,
"....getting into such a mess while her back was turned that she had no choice but the rearrange them and did they think she had nothing better to do with her time." (pg 159)
She may not be a child, but she still talks to dolls as if they were imaginary friends.
4. Bruno thinks he is moving back to Berlin. He comes to see Shmuel and they plan one last adventure together. Bruno thinks,
"All in all, it seemed like a very sensible plan and a good way to say goodbye." (pg 199)
The ironic thing is that it would be their final goodbye. They would both die taking that adventure.
5.When they were marched into the gas chamber, Bruno took Shmuel's hand and says,
"You're my best friend, Shmuel. My best friend for life." (pg 213)
The ironic thing about that statement is that it became true because they both died moments later.
6. Finally, there is the sad event. The father thinks he is killing Polish prisoners, but he unknowingly kills his son with the rest of the people.