Batman: Nightwalker by Marie Lu

Before he was Batman, he was Bruce Wayne. A reckless boy willing to break the rules for a girl who may be his worst enemy.

One by one, the city’s elites are being executed as their mansions’ security systems turn against them. Meanwhile, Bruce is turning eighteen and about to inherit his family’s fortune, not to mention the keys to Wayne Enterprises and all the tech gadgetry. But after a run-in with the police, he’s forced to do community service at Arkham Asylum, the infamous prison that holds the city’s most brutal criminals.

In Arkham, Bruce meets Madeleine, a brilliant girl with ties to the Nightwalkers. What is she hiding? And why will she speak only to Bruce? Is he getting her to divulge her secrets, or is he feeding her the information she needs to bring Gotham City to its knees?