Ten-year-old Sarah Moran of Atlanta, whose family calls Alys Beach their second home, has never been one to sit back and listen passively to books at bedtime. Instead, for years her favorite nighttime routine was inventing brand-new stories with her stepfather, Shaun Rawls.

“Sarah and I had a routine,” explains Rawls, “where I would say, ‘Will you tell me a story?’ It was kind of our thing. Some of our stories were okay and some were horrible, and then one night we came up with the story of Stella the Starfish. After we did it, Sarah said, ‘I think that could be a book.’ And I thought, ‘You know what? Maybe it could.’”

By the next day, Rawls had roughed out Stella the Starfish, a story about a starfish who is mesmerized by tales about life on land but warned by her parents to avoid the dangers that lurk there. He and Sarah worked together to tweak the details, like the inclusion of Stella’s teacher, Miss Gloria, who bears the same name as a close family friend, and a girl named Sarah who comes to Stella’s aid when the little starfish makes a daring trip to the shore.

Before long, they had chosen gifted illustrator Alexandria Gold (who also illustrated a book written by a close friend of Sarah’s mother) to draw the characters to life, and Stella the Starfish was born. Published last summer, it sold close to 400 copies in its first weeks and eventually landed on top children’s books lists for Amazon and Barnes & Noble. (Rawls and Moran are both listed as authors.)

Moran remembers one of the most exciting moments after the book’s release was the chance to share it at school, where she and the principal took turns reading pages at an assembly. “People were surprised I had written a book with my stepdad,” she says. “They asked a lot of questions, and it was fun telling them about it.”

While Moran has been making up stories for as long as she can remember, she and Rawls say the family’s shared love of the water was a big inspiration for Stella. “One of Sarah’s favorite things to do is to be at the beach, and Alys is one of our favorite places on the planet,” Rawls says. “We’ve never actually seen a starfish down there, but it hasn’t stopped Sarah and others from looking.”

He and Moran are still both amazed to see how their pastime turned into a work of art that anyone can buy and read. “It’s kind of funny—at 10-years-old, Sarah is a published author, and not everybody gets to say that. It was fun to see it come to life. It was a cool experience for Sarah and for me, too.”