It’s an exploration of the immigrant experience through the superhero genre, which is essentially all about immigrants and living in two cultures at once. As Gene says:
Superheroes are also about immigrants. Take at look at Superman, the granddaddy of them all. His parents sent him to America in search of a better life. He had two names, one American (Clark Kent) and the other foreign (Kal-El). He wears two sets of clothes and lives in between two cultures. He loves his new home, but a part of him longs for his old one.
The character originated in the 1940s and had a short run, but Gene is reviving this forgotten superhero with a new story.
I discovered Gene Luen Yang earlier this spring thanks to the Festival of Faith and Writing. If his past work is any indication (especially Boxers & Saints and American Born Chinese), this one is going to be worth checking out.