Nazi Germany is a challenging setting for a coming-of-age story, but that's the case with Markus Zusak's popular novel The Book Thief, which was turned into the film that opens in New Zealand next month.

The story focuses on children who unknowingly accept the daily images of Adolf Hitler's prewar Germany - from the Hitler Youth uniforms to the swastikas on the flags - as normal, even enjoyable, before learning their true nature.

"We as an audience know what the symbols and rhetoric of the time truly mean, and it's uncomfortable to see," said the film's director, Brian Percival, who is best known for directing Downton Abbey.

"This film is about the corruption of innocence. An entire generation of children really believed they were part of something really good and fun. They can't define what's right and wrong at that age."

The main character, foster child Liesel (played by 13-year-old Sophie Nelisse), assimilates in a German school where she happily sings a Hitler Youth song with her class-mates without comprehending the anti-Semitic lyrics. The scene's eeriness is enhanced by the stunning arrangement performed by a German children's choir.

"It's a song that sounds so beautiful," Percival says. "But when you see the translation of the words, it's just horrific. But the point is, Liesel doesn't really understand."

Percival said he had to receive Government permission to perform the song on the German set since it, and any other songs or symbols pertaining to the Third Reich, are banned in the country. Despite the emotional difficulty in performing the lyrics, the choir agreed because it felt the educational message was vital.

"We had to teach the choir to sing the song, because they had never heard this before," Percival said. "But they knew it was ultimately for a good cause."

On-screen, Liesel wears the swastika on her school uniform without thought, and the children play soccer beneath Nazi flags. Neighbour Rudy (Nico Liersch) revels in his sharp Hitler Youth uniform while simultaneously worshiping African-American track star Jesse Owens, much to the anger of Nazi officials who detest the gold-medal-winning Olympian.

A key turn in Liesel's thinking comes in a scene depicting a ceremonial book burning by the German Student Association. Shooting the scene in the town of Gorlitz was particularly emotional, since the square was draped in the banned symbol of the Nazi swastika.

"We have seen it in films before, but when you actually saw it in the square, it was quite uncomfortable," Percival said. "We shot during the night, and during the days, the insignia had to be wrapped up and covered. The flags were only revealed just before we started to film."

The book burning was difficult to watch for the predominantly German film crew.

"It had a tremendous emotional impact on everyone on this crew of wide-ranging ages, from the young runners on the set to the prop guys in their 60s," said Geoffrey Rush, who plays Liesel's foster father.

Percival saw German crew members with tears streaming down their faces.

"It was tears of shame," he said. "Because they felt responsible for their forefathers. I knew that modern German people are not proud of what happened. But while they could not exorcise their past, they at least could be involved in something that explored just how wrong what went on at the time was."

To that end, they succeeded. Rabbi Marvin Hier, the dean and founder of the Simon Wiesenthal Centre and the Museum of Tolerance, hosted a screening of The Book Thief and, afterward, called the film "an important human lesson".

"Here's a young child set in the worst place on Earth you could ever grow up in, in the heart of Nazi Germany," he said. "But it shows that even in the devil's house, it is possible to take out that evil, to have justice and goodness prevail. We tend to forget that wherever goodness plants a seed, eventually, it will take over the garden."

- The Book Thief opens January 9.