The author of the beloved Captain Underpants children's book series is apologizing for a spin-off graphic novel now being pulled from shelves over racism concerns.

Scholastic Books announced that distribution of 2010's The Adventures of Ook and Gluk: Kung-Fu Cavemen from the Future would be halted after a mutual agreement between writer Dav Pilkey and the publishing house.

"Together, we recognize that this book perpetuates passive racism. We are deeply sorry for this serious mistake," Scholastic said in a statement. That apology followed a petition by a Korean-American father, who said his two younger children were huge fans of Pilkey—but that he was appalled by the "racist imagery and stereotypical tropes" he saw in the Ook and Gluk book.

Pilkey has authored several wildly popular book series for kids, including Captain Underpants, Ricky Ricotta's Mighty Robot, and the Dog Man series. Pilkey issued an apology letter of his own for The Adventures of Ook and Gluk on his YouTube page.

"About ten years ago I created a book about a group of friends who save the world using kung fu and the principles found in Chinese philosophy. The Adventures of Ook and Gluk: Kung-Fu Cavemen from the Future was intended to showcase diversity, equality, and non-violent conflict resolution," he wrote. "But this week it was brought to my attention that this book also contains harmful racial stereotypes and passively racist imagery. I wanted to take this opportunity to publicly apologize for this. It was and is wrong and harmful to my Asian readers, friends, and family, and to all Asian people."

Dav Pilkey Apology

Pilkey said that Scholastic is ceasing all future publication of the book, as well as working to pull existing copies from retail stores and library shelves.

"I hope that you, my readers, will forgive me, and learn from my mistake that even unintentional and passive stereotypes and racism is harmful to everyone," Pilkey explained. "I apologize, and I pledge to do better."

Pilkey also added a post-script to the letter saying that he and his wife would be donating all money made from the book's advance and royalties to charity, including those designed to promote diversity in children's books and organizations that work to combat anti-Asian hate. Pilkey highlighted We Need Diverse Books and TheaterWorks USA as some of the recipients.

Scholastic isn't the first company to pull titles over racism concerns. Dr. Seuss Enterprises also recently announced a decision to stop publishing six titles it said contained racist images.

There's a good chance we'll see more decisions like this in the future, as more and more companies re-evaluate their past offerings. "It is our duty and privilege to publish books with powerful and positive representations of our diverse society," Scholastic said. "We will continue to strengthen our review processes as we seek to support all young readers."

All kids deserve to feel seen, respected and represented, and diversity in children's books is incredibly important. Diverse books can either hold up a mirror to a child's own life, or give them a window into another's—making it all the more important that what's reflected in books is free from stereotypes and tropes. Scholastic's decision is one good step in that direction, but there are many more to go.