Not in My Book by Katie Holt

Rosie, an idealistic and passionate Peruvian American, leaves her Tennessee hometown to pursue her dream of making it in New York as a writer. But her plan is derailed when she ends up in class with her archnemesis and ex-crush, Aiden Huntington—an obnoxious, surly, and gorgeous literary fiction writer who doesn’t have much patience for the romance genre or for Rosie.

Rosie and Aiden regularly go to verbal battle in workshop until their professor reaches her breaking point. She allows them to stay in her class on one condition: they must cowrite a novel that blends their genres.