Shadowshaper by Daniel Jose Older

Summer has just started, and Sierra plans to enjoy it, hanging out with her friends in their Brooklyn neighborhood and painting a mural at the local junklot. Then things start to get weird. While she is talking to fellow artist Robbie at the first party of the summer, a zombielike creature disrupts things, Robbie disappears, and she is left to discover that she lives in a world full of magic that she knows nothing about. As she slowly pieces together the mystery of her heritage, Sierra discovers her own powers of ancestral magic and battles the evil professor who is trying to steal them.  (Amazon.com)