One of Us is Lying by Karen M. McManus

Five students at Bayview High enter detention, but only four walk out alive, leaving the remaining group as prime suspects in a murder investigation involving a high school gossip app.

This book contains: alcohol/abuse, anxiety, blackmail, controversial cultural and racial commentary, cyberbullying, depression, deception, derogatory terms, discrimination, drugs/dealing, inflammatory gender and social commentary, murder, parental abandonment, parental neglect, physical assault, sexual activities, sexism, smoking, suicide attempt/ideation, theft, toxic relationships, violence and voyeurism  (themes).