What is the summary of book Pretty Little Liars?

"Pretty Little Liars" revolves around four best friends, Aria, Hanna, Emily, and Spencer, whose lives are shattered when their queen bee friend, Alison DiLaurentis, mysteriously disappears. A year later, Alison's disappearance is declared a murder, and the girls start receiving cryptic messages from an anonymous tormentor called "A" who threatens to expose their darkest secrets.

"A" knows everything about the girls' lives, including their hidden affairs, fights, and past mistakes. The messages often taunt the girls about Alison's disappearance and lead them to believe she's still alive. They are forced to confront their past, their own secrets, and their complicated relationships while trying to uncover the truth about Alison's fate and "A"s identity.

As the story unfolds, the girls navigate a web of suspicion, betrayal, and hidden identities. They uncover secrets about their families, their friends, and even Alison herself. The story delves into themes of friendship, loyalty, trust, and the dark side of teenage life.

The series is characterized by its twists and turns, red herrings, and multiple potential suspects. It keeps the reader guessing until the very end, and the identity of "A" is revealed in shocking fashion.