Here's why:
* Mystery: The central plot revolves around a missing person (the face on the milk carton) and the protagonist's quest to uncover the truth behind their disappearance. This involves clues, suspects, and twists and turns typical of the mystery genre.
* Thriller: The story often includes elements of suspense and danger, keeping the reader on edge as the protagonist faces obstacles and potential threats in their investigation.
* Young Adult: The target audience is usually teenagers or young adults, evident in the themes of identity, friendship, first love, and navigating challenging situations.
While the genre can be classified as mystery/thriller, it also incorporates aspects of coming-of-age and suspense.