The Space Between - Brenna Yovanoff

A transcendent novel about a demon girl's search for love, from the New York Times bestselling author of The Replacement

Everything burns in Pandemonium, a city in Hell made of chrome and steel, where there is no future and life is an expanse of frozen time. That's where Daphne--the daughter of Lilith and Lucifer--waits, wondering what lies in store for her. Will she become a soulless demon like her sisters? Or follow in the footsteps of her brother Obie, whose life is devoted to saving lost souls on Earth? But when Obie saves a troubled boy named Truman from the brink of death and then goes missing, Daphne is catapulted on a mission to Earth, with Truman as her guide. As Daphne and Truman search for Obie, they discover what it means to love and be human in a world where human is the hardest thing to be.