Tropesick by Lauren Okie

Katie Caruso is a completely normal 25-year-old girl. She likes glitter and sequins and flirting with cute boys at bars. She's also a proud ghost-writer for Meredith Bradford, the bestselling romance novelist of all time. Tyler McNally is a sleeve-tattooed, Ivy League-educated aspiring literary fiction novelist who literally can't think of anything worse than romance novels, but whose agent forces him to agree to ghost-write one. When the pair meet to begin work, each is as stunned as the other to see who their writing partner is meant to be. Connected by a shared tragedy, the pair are ex's, who haven't seen or spoken to each other since the overdose death of Katie's older brother. Tyler was her brother's best friend, and Katie, naturally, was the girl next door. As the summer unfolds they soon discover that dozens of classic romance tropes, including the ones they're crafting on page, are mysteriously playing out in their real lives.