The Only Child was selected in 2015 as a New York Times Best Illustrated Children's Book.

The wordless picture book depicts Guojing's memories of her "loneliness and isolation" during childhood, as she was often left alone at home when her parents go to work — a reality her generation had to encounter under China's one-child policy in the 1980s. The imaginary and dreamy storyline helps minimize the tone of the loneliness.

The little girl dozes off on a city bus on her way to her nainai's house and wakes in an unknown forest. She bonds with a flying deer, enormous whales, and a seal pup while in the clouds. Eventually, the deer carries the little girl back to her nainai's. Guo does not adopt a critical attitude towards the policy, rather, she shows her optimistic mood and resilience, as she puts on the front page, "there is always a path...guiding the way back home".

The illustrator provides an absolute visual delight to readers. Guo draws smoky and mystical-looking pencil drawings that create strong surges of nostalgia for the 1980s.

She also adds a couple of vivid details with the use of a comic-strip oriented setting. In the story, the fluffy softness of clouds, the warmth of the stag's closeness, provides comfort for the little girl, as it does for the readers.