The Bones Beneath My Skin by TJ Klune

A thrilling and heart-healing supernatural road trip featuring an extraordinary young girl and her two unlikely protectors. The Bones Beneath My Skin is a gripping tale that explores what it means to be human.
 
In the spring of 1995, Nate Cartwright is at a loose end: his parents are dead, his older brother has disowned him and he’s been fired from his job. Looking for a sense of direction, he returns to his family’s summer cabin in Oregon. The cabin should be empty – but it’s not.

Inside is a man named Alex and an extraordinary little girl who calls herself Artemis Darth Vader. There’s far more to Art than meets the eye. But as Nate and Alex bond over just how special she truly is, they discover that powerful forces are closing in – forces that want nothing more than to control her...

There’s nothing more human than a broken heart.