(2) Sea Level
You don't have to be a historian of the Holocaust to understand the events surrounding The Boy in the Striped Pajamas—most of the action takes place near Auschwitz, but the book generally steers clear of nitty gritty details like dates, names, procedures, weapons, and geography. On top of that, the language is simple (we're talking nine-year-old levels of complicated) for the most part, with short dialogue and a pretty to-the-point approach.