The Twin Stars by Bridgette Dutta Portman

A magical journal. A world savaged by its own suns. An evil prince. A princess in hiding. And a teenage girl who learns to be the hero of her own story. Sixteen-year-old Olive Joshi has obsessive-compulsive disorder, and can't stop worrying about hurting the people she loves. She finds refuge in writing about Coseema, a magical princess on a distant planet. Coseema is fearless, confident, and perfect - everything Olive thinks she’ll never be. When she falls through a portal into her own unfinished story, Olive finds herself in a world in peril: double suns scorch the land, the brutal Prince Burnash seeks supreme power, and Coseema is nowhere to be found. Together with her friends - a bold poet, a cursed musician, a renegade soldier, and an adventurous girl from the desert - Olive will have to face her deepest fears to find the hero in herself. An engrossing new portal fantasy in the spirit of the Wizard of Oz, the Neverending Story, and the Chronicles of Narnia.​