The Boy in the Striped Pajamas: A Fable (2006) by John Boyne is a small book with incredible impact.
I have never read a book about the Holocaust from a small boy's point of view let alone the son of the commandant of Aushwicz. I was blown away.
Bruno and his family move to a small town in Poland from Berlin when his father is transferred because "the Fury has big plans" for Bruno's father. Bruno at nine is terribly naive, but this well written story allows you to understand that as a sheltered child of an officer - he would not know or understand what is really going on. Bruno has no friends where he now lives. Over a long time (in a child's time) he becomes friends with a small boy that wears striped pajamas. Bruno does not understand why he cannot go on the other side of the fence to play with his new friend and the hundreds of children he knows are over there.
I understand that there has been a lot of negative critical comments about the subject manner and Bruno's being so naive. To me that is part of the message of the book - that in the midst of horror a child's innocence brings hope and that bigotry is learned and not innate.