How is the theme "Hope" developed throughout the story of the Glass Castle?

I'm not sure that hope is really an underlying theme. As children, hope, is merely an illusion. The title of the book and a major theme within it, the Glass Castle represents Rex's hope for a magical, fantastic life in which he can provide for his family and please his children. The Glass Castle, however, is merely a dream. Even a metaphor for the glass Castle is a fantasy. The Walls parents are incapable of providing any stability for their children.