What is the theme in Moon Over Manifest by Clare Vanderpool?

Secrets and grief make up a major theme of the story. Abilene comes to a Manifest that is greatly changed from the days in which her father lived there as a boy. Abilene remembers everything about her father's stories of the town, but finds that time has not been kind to Manifest and that the people are not as open and friendly as she had expected. However, as Abilene's time in Manifest grows, she learns more and more about the past the town has hidden away.