Sky of Dreams by Kate Renae

What if mental illness was a sign of rare magic?

Kenya Sawyer sees herself as broken. In the struggle against her own mind, she’s always been afraid she’ll jump and fall.
She never expected to jump into another realm entirely.
Two years after the murder of her best friend, Lia, Kenya returns to San Francisco.
She isn’t exactly met with open arms. Lia’s twin brother, Luka, still hasn’t forgiven her for leaving, and the memory of Lia is everywhere.
As Kenya tries to return to a normal life, her mind begins to spiral. She’s plagued by vivid dreams: a city of magic, Lia trapped and begging for help, and a violet sky of dreams… and nightmares.
Kenya thinks the images are proof of her broken mind — until she and Luka accidentally fall into a realm with that same violet sky. There, they learn that Kenya has magic: realm-jumping magic that no one has seen for five thousand years.
Suddenly, it’s possible that Lia could still be alive, trapped in this new realm. As Kenya and Luka explore a city of magic to find her, they ignore the feeling that something has changed between them, something beyond childhood affection. But what they need to do is keep each other alive, because if they don’t focus on finding Lia, they may get pulled into wars and worlds they never imagined.

That is, if the broken trust between them doesn’t prove deadly first.