The allegory of the family
This family is undergoing an allegorical experience that only a few people know about from experience: their son is autistic, and their experience of life is forever altered by this. They love him, but they don't know what his life is like, and it's hard for them to face the loss of freedom that this fate entails. The story can be seen as a metaphorization of that emotional journey. They end by questioning the universe in a mystic, supernatural way.
The Mojave
The desert is not part of their normal daily life. Instead, they travel to the desert, making the desert an even more obvious symbol. Broadly, it symbolizes chaos. That's why when Raj disappears, the family is unnerved and undone. They don't know what the chaos of the universe might do to their Raj, and when he returns unscathed, completing a hero's journey, they are amazed. They thought for sure his autism would have made him unsuitable for such a venture, but they were wrong.
The hero's journey
Raj is a hero in the novel, because he departs from his family and comes back from his desert wandering with a new aspect. The parents struggle to make sense of this subtle transformation, but they suspect Raj is forever changed. They begin to look toward nearby religious myths about the desert to learn more about the desert's capacity to change people who survive passage through it. Raj is heroic, even though he is differently abled, and the family is able to see that he is not as needy as they suspected.
The Coyote
While learning about the desert, the family learns about the mythic Coyote, an agent of change who is also known as an archetypal trickster. The idea of a godlike trickster helps them understand the desert's transformative power, because the change has the ba-da-bing, ba-da-boom reversal of a clever riddle or joke. Broadly, the Coyote represents the universe's fateful quality, because they sometimes feel like the butt of a divine joke. The Coyote helps them concretize their feelings about this.
Mythology as a symbol
In the story, mythology can be seen as a symbol. The family longs for answers that are difficult to see from their limited point of view. By examining myths, they broaden their point of view by combining it with various communities and cultures who have faced the same mythic burdens and trials as the family. They learn that they are part of a network of humans all experiencing fate together. Myth is a tool for their enlightenment and their surrender, because the myths help them to accept fate's power in their lives.
