Jane Yolen died Thursday at 87 in her home in Western Massachusetts, closing a career that helped define modern children’s literature. Her daughter, Heidi Stemple, said Yolen had “passed gently with no pain or stress” and was with family when she died.

The death lands hard because Yolen was not simply prolific; she was durable. She published more than 100 titles for young readers before she ever wrote the book that made her a signature name, then went on to publish 450 children’s books in all. Her 450th title appeared just this year, a marker of how long she kept working and how little her output slowed.

By the time The Devil’s Arithmetic appeared in 1988, Yolen was already an award-winning author and illustrator. She had won the Caldecott Medal for Owl Moon in 1987, but the Holocaust time-travel novel became the book most readers still associate with her. It won immediate acclaim, picked up multiple awards and remains in print. It was later adapted into an Emmy Award-winning Showtime feature starring Kirsten Dunst, extending the reach of a story that found a place in classrooms as well as libraries.

What made that book notable was the path to it. Yolen did not start out eager to take on a Jewish children’s book; she said she did not think she knew enough about Judaism to write one. Then she turned in a first draft after a spark of an idea about a Holocaust time-travel fantasy, and the result became a different kind of Holocaust book, in the words of Norman H. Finkelstein. He said Yolen did a superb job of bringing the Holocaust down to a level that ordinary American kids could understand, with characters that felt real rather than cut out of paper.

That balance is why the search for who died today will keep circling back to Yolen. She wrote widely across childhood and faith, including the How Do Dinosaurs … series and How Do Dinosaurs Say Happy Chanukah?, but The Devil’s Arithmetic is the book that fixed her place in the culture. The unanswered detail is the cause of death, which has not been made public, but the larger fact is clear: one of the most productive voices in young readers’ books is gone, and her most enduring work is likely to keep doing what it has done for decades.