In 2012, Kwame Alexander was struggling to sell “The Crossover,” a hip-hop inflected novel in verse about twin brothers who are stars of their junior high school basketball team. Twenty-two publishers had rejected it. Most said there was no market for a poetry-infused, sports-themed children’s book, because boys wouldn’t read poetry, and girls wouldn’t read about sports.

Undeterred, Mr. Alexander was planning to self-publish it, when Houghton Mifflin Harcourt made him an offer. “The Crossover” became an instant critical and commercial hit. It won the prestigious Newbery Medal in 2015, and has sold nearly 500,000 hardcover and e-book copies, cementing Mr. Alexander’s reputation as one of the country’s most innovative children’s book authors.

Now, Mr. Alexander is poised to have an even bigger impact on contemporary children’s literature. Next spring, he will begin publishing books under his own imprint, Versify, at Houghton Mifflin Harcourt Books for Young Readers, and he’s looking for risky, unconventional books like “The Crossover,” he says.

“My inclination is going to be to find books that other people might not view as feasible or doable,” he said during an interview at his publisher’s office. “I feel like I’m the guy to do that.”