Here's why:
* Young Adult: The main characters are high school students, and the story deals with themes relevant to teenagers.
* Thriller: The book is filled with suspense, danger, and a sense of unease as the mystery unfolds.
* Mystery: The plot revolves around a central mystery: the disappearance of a girl and the subsequent events that follow.
* Romance: There are romantic relationships between the characters, adding another layer to the story.
It's important to note that while these are the primary genres, other elements might be present. For example, the book could also be considered a coming-of-age story as the characters face challenges and learn about themselves.