Many academic studies, and some overseas works, notably Leslie T. Chang’s “Factory Girls,” have focused on the special challenges facing female migrant workers as they grapple with new freedoms in the cities. Yet Ms. Sheng’s technique of writing through, and about, women’s bodies, is unusually intimate and direct. Her choice of a striking physical attribute for Ms. Qian — unusually large breasts — highlights what she says is a serious issue: How can a poor woman who attracts considerable male sexual attention hold on to her morals in a highly amoral society?

“I wanted to give these girls an exterior sign to symbolize their worries and anxieties as they head into China’s urban society,” Ms. Sheng said.

Ms. Sheng knows her characters intimately, having grown up with women like them in a village in the southern province of Hunan. She, too, headed for the southern economic boomtown of Shenzhen in the 1990s. She held several jobs over seven years, including at a securities company and a magazine, before leaving to write full-time in 2001.

Her exploration of women’s bodies and how they shape their destinies leads her into new literary territory, says the reviewer and poet Ma Ce. “‘Northern Girls’ is about bodies and freedom, but more importantly, it’s about the limits to that freedom,” Mr. Ma wrote in an essay.

Qian Xiaohong’s breasts are a boon and a burden. “Like pomelos, while those of her best friend, Li Sijiang, are like tangerines,” Ms. Sheng said. “Of course, a woman with pomelos is going to have a harder time in society than a woman with tangerines.”

Yet Ms. Qian, eager to grasp her freedoms, enjoys her sexuality. This is established on the first page of the novel, as rendered by the Beijing-based translator Eric Abrahamsen: “All the decent girls in the village wore loose clothing and hunched their shoulders — protecting their chests was the first step in protecting their reputations. Only Qian Xiaohong walked with her mounds thrust forward, bearing down mercilessly, like dark clouds threatening a city.”

The focus on female bodies leads to harrowing territory, too. Ms. Li is seized by officials in a small town during a family planning crackdown, taken to a hospital and forcibly sterilized.