The last thing Phoebe Zito wants is to be noticed. The newest kid at Sally Ride High School, newly arrived in Los Angeles, and newly transitioned, she's just trying to blend in while she figures out exactly who she is. But with her mom checked out, her dad still adjusting to having a daughter, and no guidebook on how to be a girl, that isn't going to be easy.

Enter Mackenzie Ishikawa. She’s the girl who all girls want to be, and all the boys want to be with—and, Mackenzie has decided, Phoebe's new best friend. Mackenzie knows what it takes to survive and thrive as a girl in high school, most of all that no matter who Phoebe wants to be, or who she wants to date, she's going to need someone having her back.

Phoebe soon realizes what Mackenzie knows too well: Being true to yourself is going to mean breaking some hearts. But as Phoebe discovers what kind of girl she is—and what kind of girl everyone around her thinks she's supposed to be—she worries one of those hearts will be her own.