One of Us is Lying by Karen M. McManus
Five teens have detention one day:
Bronwyn - the valedictorian and general "little Miss Perfect"
Cooper - the jock destined for the MLB
Addy - the popular girl dating the football hero
Nate - the criminal "bad boy"
Simon - the person who runs the school's gossip app 'About That'
By the end of detention one of them is dead and the rest are suspects.
This book was a lot of fun and very hard to put down. The mystery actually had me for a decent amount of the book, which is hard to do. I'd highly recommend it.