What is the Main idea of the story

If you are looking for one main idea, and this story encompasses more than one..... I'd have to go with the theme of broken promises. The Glass Castle is someone's story.... it's a story of childhood and family dysfunction. It's a story of parents, who didn't understand what it meant to parent..... it's about the broken promise of a real home, which in turn, aludes to the family that never really was. The glass castle was never built, but a home isn't really a place.... a home is the people who live in it.