Fear Street: Secret Admirer by R. L. Stine

Selena has it all. She just scored the lead in her high school play, and everyone adores her. So when she starts receiving dead flowers from a secret “admirer” named The Sun, she just assumes it’s a harmless fan.

But Selena soon realizes that The Sun is serious...dead serious. First, her understudy is injured in a suspicious accident. Then, a speeding car almost kills her! Selena doesn’t know what this psycho wants. All she knows is that her number-one fan has become her number-one nightmare.