https://www.snopes.com/fact-check/book-wicked-gregory-maguire-explicit/

In a 2014 interview, he commented, "I deliberately included a ribald, unappealing sex scene in the first 10 pages so people would know it was not for children."

https://www.publishersweekly.com/pw/by-topic/childrens/childrens-authors/article/63887-q-a-with-gregory-maguire.html