Others were on crutches and many had bandages around their heads. Some carried spades and were being led by groups of soldiers to a place where they could no longer be seen. (4.192)
With the ominous images of "crutches'" and "bandages," as well as the fact that soldiers are leading people to a place they can't be "seen," we're pretty sure nothing good is happening at Auschwitz. Even if we knew nothing about history (like Bruno), the dark mood is enough to make us uncomfortable.
"Those children look like they've never had a bath in their lives." (4.198)
Gretel makes this observation when Bruno shows her the children he sees from his bedroom window. She offers a rare glimpse into prisoner life—and it ain't pretty. We are totally going to feel grateful for our shower the next time we step into it.
[…] the very last things they owned were put into suitcases and an official car with red-and-black flags on the front had stopped at their door to take them away. (5.208)
The contrast between how Bruno's family is moved to Auschwitz and how Shmuel's family is forced to go there is staggeringly different. For Bruno and his family, their items are packed by the help, and then they're driven by official cars to a nice, comfy train. As we later learn, Shmuel's family got there by far less pleasant means.
"We should have never let the Fury come to dinner […]. Some people and their determination to get ahead." (5.210)
Yes, it probably wasn't the best idea to have Adolf Hitler to dinner--Bruno's mom is right about that. But when it comes to the family decisions, anything "some people" (a.k.a. Bruno's father) wants is what he gets.
"This is my work, important work. Important to our country. Important to the Fury. You'll understand that some day." (5.254)
Bruno's father explains why they are in Auschwitz to Bruno, but if you ask us, it's a pretty weak excuse, especially considering Bruno doesn't know who "the Fury" is or what's going on in Germany.
"War is not a fit subject for conversation." (7.358)
Really? Really? We're not entirely convinced that keeping kids in the dark about what's happening in the world (especially in their own country) is the best idea. Then again, ignorance is bliss.
"He runs the country, idiot […] don't you ever read a newspaper?" (11.638)
You know, we wonder the same thing ourselves. Why is it that Gretel reads the newspapers but Bruno doesn't? He may be nine-years-old, but he's old enough to read a paper, right?
"And every time we left the house, [Shmuel's mother] told us we had to wear one of these armbands." (12.695)
Shmuel relates his experience to Bruno of being forced to wear armbands with the Star of David. Bruno doesn't understand the significance of it, though, and instead considers Shmuel lucky to have been given an accessory. Yeah, Bruno really doesn't get what's going on here…
[Shmuel] turned and walked away and Bruno noticed again just how small and skinny his new friend was. (12.748)
As the days pass, Shmuel gets smaller and skinnier, something Bruno notices but doesn't question. It's clear, though, that one of the warfare tactics being used on Shmuel is denial of enough food.
[…] they were all piling into a long room that was surprisingly warm and must have been very securely built because no rain was getting in anywhere. (19.1303)
This is one of the last scenes of the novel, and in it, Bruno and Shmuel are packed into a gas chamber with other Auschwitz prisoners. Even though this was a common way to kill people during the Holocaust, we're still left pretty shocked.