“I give a careless shrug so Dodie won’t see how nervous I am about the officials. And how much I’m desperately hoping Mother Minka remembers the story we agreed on about my parents. About how they were killed in a farming accident. Tragically.” 

The story that his parents and Mother Minka came up with is designed to shield Felix from the knowledge that his parents are likely in a concentration camp, and to protect him from Nazi inquiries. Felix later admits that this story saved his life. However, not knowing the truth is what causes him to leave the safety of the orphanage.

“‘And Adolf Hitler?’ I whisper. ‘Father Ludwik says Adolf Hitler keeps us safe too.’”

Felix ironically invokes Adolph Hitler in his prayers. This is derived from Father Ludwik, the head priest at the orphanage. Whether Ludwik is actually a Nazi sympathizer or is faking it is unclear: Swearing allegiance to the Nazis would keep his Catholic orphanage safe. 

“There’s a gang of thugs going around the country burning Jewish books. Mum and Dad, wherever in Europe they are, probably don’t even know they are in danger.”

Felix is not yet able to correlate the Nazis with atrocities larger than book burning. He is unaware that it is not the fact that his parents are booksellers but that they are Jewish that puts them in danger. He wants to try to hide his parents’ books.