Pretty Little Liars

Rosewood, Pennsylvania, is a wealthy suburb where Spencer, Hanna, Aria and Emily once formed a tight circle around Alison DiLaurentis, the friend who led them all. When Alison vanishes, the group falls apart and the girls go their separate ways.

Three years later, each of them starts getting threatening messages from someone who signs only as "A". The sender knows secrets that, until now, only Alison could have known.

The messages turn more menacing, and the four are pushed back into each other's company. Each has something to protect. Spencer hides her rivalry and ambition, and Hanna hides her hunger for popularity along with habits she keeps out of sight. Aria carries a secret from a family trip, and Emily is unsure about her own feelings.

This is the first book in the Pretty Little Liars series, published by HarperTeen in 2006. It blends teen drama and romance with a mystery that builds slowly around the identity of A and the extent of what A knows.