This is a complicated question. One aspect of the question is the most literal one. It is not a diary of a specific girl who struggles with drug use and addiction. Sparks wrote it. Sparks worked with teens in different forms and wrote the book in the guise of a diary from a teen. In this light, the book is not real. Yet, there is much in the book that is real. Sparks wrote her book based on her interactions and work with teens who struggled with drug use and addiction. While there might not be a child who actually wrote the diary, the characterization that Sparks achieves is quite real and the reality in which the protagonist is placed is also quite valid and authentic. In this light, the narrator is more of a tableau of teens whose experiences with drug use and abuse is powerfully compelling. Sparks is convinced that the story of Alice is a true one and that drug use and abuse contains no redemption, and this becomes the haunting truth in the book and about the topic. This is real.