Some of the books in the "Pretty Little Liars" series by Sara Shepard include "Pretty Little Liars," "Killer," "Wanted," "Stunning" and "Vicious." There are also two supplementary books that tell alternative accounts from the antagonist's perspective called "Pretty Little Secrets" and "Ali's Pretty Little Lies."
The first novel, "Pretty Little Liars," introduces Alison, Aria, Emily, Hanna and Spencer. Three years before the action of the book, Alison disappeared. The girls start receiving threatening and incriminating text messages alluding to major secrets from someone called A, and Ali's body is found buried in her own backyard.
In "Killer," Hanna is chasing a popular sophomore, Aria is trying to find out more about her boyfriend's past, Spencer is stealing from her family, and Emily is shunning her family's demands while dating a female classmate. They thought they knew who A was when Ali's killer was arrested, but they are still receiving texts. In the book "Stunning," the girls are hoping to forget about everything Ali did to them, but A keeps reminding them of all the ways she ruined their lives. A drags out every bad thing the girls have ever done, threatening to disrupt their lives forever. In the series conclusion, "Vicious," the girls work together to bring A to justice, and what they discover destroys everything they thought they knew about Alison DiLaurentis.