It's a story about a character getting possessed and the chaos that occurs as a result so theres lots of violence/horror surrounding that. Book takes place in the 80's in the southern US, so there are some racist/bigoted school activities (during spirit week they have slave/owner day where one student "owns" another for the day and can make them do whatever they want; one character briefly mentions being in blackface while performing a "We Are The World" type performance during a school concert)

Students take LSD at the beginning of the book (drug use). Characters attend a religious (Christian) private high school, so religion is used to influence the kids (while describing sexual assault a teacher says something along the lines of 'you don't want God's gift (virginity) to be taken away bc you can't get it back'; Satanism is talked about a lot by the students and teachers). Possessed character is really sick at first, and mentions having her period for 2 weeks (descriptions of bloody pads in the trash). While possessed she goes on to trick one of her friends into eating tapeworms (they become really sick as a result- vomiting, body horror), writes fake letters to have another friend fall in love with the school chaplain (adult/minor relationship), and bullies her best friend. She shoots and kills her pet dog as well. At first her best friend thinks she may have been raped by a classmate, so sexual assault is focused on in a couple of chapters. After exorcising the demon, the formerly possessed character describes a suicide attempt. At the end of the novel they describe the course of their lives and mention parents dying, and one of the characters ends up dying of a terminal illness at the end.