Darkwater by Catherine Fisher

Description

What would you sell your soul for?

Sixteen-year-old Sarah Trevelyan would give anything to regain the power and wealth her family has lost, so she makes a bargain with Azrael, Lord of Darkwater Hall. He gives her one hundred years and the means to accomplish her objective–in exchange for her soul. Fast-forward a hundred years to Tom, a fifteen-year-old boy who dreams of attending Darkwater Hall School but doesn't believe he has the talent. Until he meets a professor named Azrael, who offers him a bargain. Will Sarah be able to stop Tom from making the same mistake she did a century ago?

This is smart fantasy mixed with elements of horror from master storyteller Catherine Fisher. She says, “Darkwater Hall is an image of the power and knowledge we all desire. But what will we pay for them, and are they worth the price?”