The Nightmare Room #8: Shadow Girl by R.L. Stine

You hold in your hand the key to a shadow world of shivers and screams. Take a step away from the safe, comfortable world you know. Unlock the door to terror. There's always room for one more in . . . The Nightmare Room.

Take a look at Selena Miles sitting in the park across the way. She looks bored, doesn't she? That's because she thinks nothing exciting ever happens to her. But Selena is about to learn the truth about herself -- her real identity, and her super powers. Too bad her powers come with a price. Selena has an archenemy who wants her dead. Maybe boring was better, but it's too late. Selena's crossed over into The Nightmare Room.