This is classic Y.A. fiction revolving around privileged teen-age girls. Petty rivalries and jealousies, pressure to excel (from parents), to fit in (from peers). Plus the added angst of having a secret that could destroy their lives and someone who knows the secret and threatens to tell. The four girls have no idea who knows and who they can trust, they don’t even trust each other.
This is a typical Y.A. book, easy to read and follow, the plot was predictable at times but the storyline is good enough to carry you through to the end. Secrets are slowly unfolding during each book. As more gets revealed, the more the mystery of who “A” is grows.