The ending is pretty tragic, because it's basically Asher being cast out of his community and shunned by his parents. Not a great start to a career, huh?
I came out of the apartment house. It was cold and dark. I looked up. My parents stood framed in the living-room window. I hailed a cab and climbed inside. It pulled slowly away from the curb. I turned in my seat and looked out the rear window of the cab. My parents were still watching me through our living room window. (369.2)
The ending emphasizes one of the book's themes, which is the struggle between individual and community. All his life, Asher has depended on his community to make him feel included and whole. But when his artwork is difficult for other members of the community to accept, he's got to break free and deal with the fact that he's an individual who must strike out on his lonesome—especially if he wants to be an artist.
In showing us his final interaction with his parents before leaving Brooklyn for good, the ending of the book yanks at our heartstrings, and for a good reason: good endings are supposed to make us feel something. In this instance, Asher feels the pain of leaving his parents and his world behind, and the uncertainty of having to be on his own for the first time in his life. His future looks hazy and confusing and his past looks like one big disaster.
Perhaps the most important aspect of this ending is the fact that Asher turns around in the cab to see that his parents are still watching him out the apartment window. This leaves the reader with some hope that, although there is a major ideological rift between Asher and his family, his parents will always love him and watch out for him.