The Book Thief
by Markus Zusak
We know next to nothing about Liesel's father. Liesel has no memories of him, but has heard he was a communist. The German Communist Party (KPD) was a legitimate political party in Germany when Hitler took power. As a popular party, members were seen as a threat to the Nazis. The novel implies that something bad happened to Liesel's dad because of his communist political views.