As kids, Junot Díaz’s goddaughters asked the author for a children’s book that reflected their experiences as Dominican girls living in the Bronx. “I’ve always had this over my head,” he said, according to The New York Times. “They asked me if I could write them something, and foolishly, I said yes.” It took more than 20 years, but Junot – who’s famously known for procrastinating and writing at a glacially slow pace – has finally come through. Titled Islandborn, the picture book follows Lola, a young Afro-Latina girl who immigrated from the DR to Washington Heights.

In school, Lola’s assigned to draw a picture of where her parents came from. But having left the island as a baby, she can’t conjure up a clear image. Instead, she turns to her family members and asks them to share their stories. She learns about their happiest moments in the DR, as well as the darker parts of the country’s history. Through their anecdotes, she creates a picture.

Though Junot’s first children’s book is aimed at 4- to 8-year-old children, Islandborn touches on immigration, struggling to find a place of belonging, and identity. These are recurring themes in his books. “It ties to my own Dominican immigrant heritage,” he said, adding that growing up, he didn’t see himself in books. “It was an absence I felt acutely.”

The book may not have come together if it weren’t for a trip to Miami. About a year and a half ago, Junot was driving with a friend, her young daughter, and his partner, Marjorie Liu. The girl demanded to hear a story, and Díaz made one up right on the spot. Liu recorded him, transcribed the story, and urged Junot to release it. But the author didn’t think it was up to snuff. “I was my typical curmudgeonly self,” he said. So Liu sent the video off to Junot’s agent, Nicole Aragi, who also encouraged him to turn it into a children’s book. He completely reworked the story, but it eventually became Islandborn.

The book, which is illustrated by Leo Espinosa, will be released next spring. And though Díaz’s goddaughters are now in their late 20s, they’ll surely appreciate that the promise was fulfilled.