Just for fun, I decided to search book titles with the keyword "stepmothers" on the Politics and Prose website. Here are the top titles I found on the first page of search results:
I'm glad to see Tales of Virtuous Stepmothers as the third result on the list. The rest of the books are a mixture of manga, drama and nonfiction genres. If you have any other ideas about stepmother book trends, share them in the comments below.