In the novel The Devil's Arithmetic, one of the most important themes is that of the importance of remembering. When Hannah Stern has to go with her mother to the Seder dinner at her grandparent's house, she protests because her friend celebrates the Christian Easter holiday with candy. Hannah doesn't understand why she can't stay there rather than go to the Seder dinner and listen to the constant talk of the past - her grandparent's experiences as Jews under the Nazi regime, particularly that of her grandfather. She doesn't understand why he can't just get over it and move on.
When she experiences first-hand the Jewish tribulations, though, as Chaya, she sees how atrocious the acts committed by the Nazis truly were, and during her time there learns that those left have to remember what happened both to honor the resiliance of the living and the dead and to prevent something like that from ever happening again.