YA Book Club for Adults - One of Us Is Lying

One of Us Is Lying by Karen McManus

One of Us Is Lying is the story of what happens when five strangers walk into detention and only four walk out alive. Everyone is a suspect and everyone has something to hide.
Bronwyn, the brain, is Yale-bound and never breaks a rule. 
Addy, the beauty, is the picture-perfect homecoming princess. 
Nate, the criminal, is already on probation for dealing.
Cooper, the athlete, is the all-star baseball pitcher.
And Simon, the outcast, is the creator of Bayview High's notorious gossip app. 
Before the end of detention, Simon's dead. And according to investigators, his death wasn't an accident.