“These are very difficult things for girls to talk about,” says Valorie Lee Schaefer, the book’s author, who had previously been a copywriter for the American Girl Doll catalog. “We were thinking, ‘We can normalize this conversation. We can give girls words to use, we can tell them some of the things they’re thinking about are absolutely normal, all the things that make young girls feel like, I’m a freak.’”

The long-term risks of early puberty

The company held focus groups, and found that tween girls were curious not only about their periods, but also about when they should start wearing a bra and how they should deal with pimples that popped up out of nowhere overnight. Schaefer says the company took this feedback, as well as the letters, and used it to develop the book’s structure, targeting it explicitly toward younger girls about to experience puberty, not preteens already in its throes. It begins with friendly tips on hair care, and then slowly progresses to more advanced physical and emotional changes and other challenges encountered by this age group, including how to identify the onset of eating disorders. “A girl of 7 doesn’t wonder about the same things a girl of 12 or 14 does,” Schaefer says. “So just meeting a girl right at that place—7, 8, 9—was what we tried to do.”

The company consulted a pediatrician to make sure the information was medically accurate, and Schaefer wrote the text in a deliberate, reassuring tone, one she called the “trusted, cool aunt.” “It wasn’t your mom or dad’s older sister,” Schaefer says. “It was probably their younger sister, someone with a few years under her belt, but also someone who wasn’t so out of touch with her adolescence that she couldn’t remember what a confusing time that was.”

That cool-aunt tone was also reassuring to parents. Many parents I spoke with for this article said they chose to give the book to their daughters because they recognized the American Girl name and thought the book was age appropriate. Lisa Goldschmidt, an attorney who has two daughters and lives in Wayne, Pennsylvania, remembers standing overwhelmed in front of an adolescent-health section at a bookstore, looking for a good resource for her then-9-year-old daughter. Some books, she says, were written for parents and were too clinical. Others didn’t seem detailed enough. But The Care and Keeping of You “struck the right note between chatty and serious in an approachable way.” She gave it to her elder daughter, who immediately handed it back to her. She had already read the book and giggled over the illustrations with friends at a sleepover.

Every woman I spoke with who grew up reading the book remembers something a bit different. Jensen McRae, a 20-year-old student at the University of Southern California, first read the book as a 10-year-old and, along with her friends, often flipped back to the breast-development page, which shows five illustrations of a topless girl standing in front of a sink. In the first, the girl is flat-chested, and in the last, she has round, developed breasts. When she learned about puberty at school, McRae remembers her teacher spinning a metaphor about how some students would have “grapes” and others would have “watermelons.” “So the book was definitely more informative than that,” she says.