Blood & Breath by Qurratulayn Muhammad

Evan Wilde is a poor working-class girl. She writes contracts on behalf of wealthier folks who want to exchange a bit of their life for minor deals with devils. It’s not until she is bleeding out, the unwilling victim of an outlawed contract sacrifice, that Evan draws a contract for herself: A devil can take the last of her life―all she wants is revenge.

With the help of a devil named Jack, Evan infiltrates the upper class by posing as one of their own to bring them down from the inside.

For the first time, Evan finds friends and maybe even love. And with time she realizes that for all their corruption, the upper class’s magic is what keeps the devils at bay. Can she condemn the world to ruin to satisfy her need for vengeance?

But a contract cannot be broken, except at a devil’s mercy. And Jack has none.