Onyx Storm (2025), a romantasy novel by Rebecca Yarros, sold 2.7 million copies in its first week, making it the fastest-selling adult fiction book in 20 years. Although the novel is categorized as adult fiction, many of Yarros’s books appeal to teenage readers, and they are sometimes considered to be young adult (YA) literature. Romantasy is a genre of popular fiction that blends romance and fantasy elements.