How does the author use symbolism in the novel, Milkweed?

The author uses the angel tombstone to symbolize the invisible world of faith and spirituality. Though the other boys do not believe in angels, Misha finds hope in the stone replica of the celestial being. With so many other things in his life disappearing, including his home, family, and food supplies, Misha finds comfort in returning to the cemetery to visit the angel. It allows him to believe that the things inside of him, his faith and his happiness, are real and cannot be harmed by the oppressive powers that seek to destroy his life.