Bruno's family represents a boiled-down cross-section of German society, with Father as the party loyalist, Mother as the naive, apolitical bystander and Gretel as the gullible young acolyte. Bruno is the nation's innocence, temporarily occupying the eye of the storm, unaware that destruction is slowly moving in over him.
Watching the family gradually realize that Father is up to something extremely sinister is the most engaging aspect of the film. Over the weeks and months, Mother (Vera Farmiga, "Joshua," "The Departed") starts to unravel, while Gretel overcompensates by investing almost religious faith in the party by hanging propaganda posters around the house and trying to convince everyone that things are just great.
It's clear that the family, as a metaphorical Germany, is in its own ideological prison. Once committed to its horrible course of action, no one can admit it's all been one step after another toward political and moral oblivion.
The plot feels contrived at times, and more resources could have gone toward developing the friendship between Bruno and Shmuel. But despite a few minor shortcomings, "The Boy in the Striped Pajamas" provides a relevant commentary on the destructive consequences of ideological blind faith, especially when that faith comes to be driven solely by fear.