YA Addicts discussion

Hey guys, I read a book a while ago that was a thriller/mystery/suspense teen book and it was really good but I can't remember what it was called! It was about a group of kids being blackmailed by a mysterious person texting them that they know their secrets and the journey of the kids to find who it is before their secrets are shared with the world. Please help:)

IS IS PRETTY LITTLE LIARS