Sure is. It's a fictional story with created characters and plotlines. The events and situations presented in it are not based on real-life events but are the product of the author's imagination.
Partly. While it's not a direct account of a specific true story, it incorporates elements and themes drawn from real-world situations and common struggles faced by teenagers.
The setting of Thirteen Reasons Why is a contemporary high school and the surrounding community. It gives a realistic portrayal of the social dynamics and challenges faced by teenagers in such an environment.