Ali said that secrets were what bonded their five-way best-friendship together for eternity. If that was true, they were going to be friends for life.
-- Narrator (Prologue)

Importance: This quote is important because it introduces the topic of secrets, which is a major theme of the novel.

They all loved Ali to death, but they sometimes hated her too -- for bossing them around and for the spell she'd cast on them. Sometimes in Ali's presence, they didn't feel real, exactly. They felt kind of like dolls, with Ali arranging their every move. Each of them wished that, just once, she had the strength to tell Ali no.
-- Narrator (Prologue)

Importance: This quote is important because it describes the complicated and dysfunctional relationship the girls have with Alison before she disappears.

She was perfect. Beautiful, witty, smart. Popular. Boys wanted to kiss Alison, and girls – even older ones – wanted to be her. So the first time...
-- Narrator (Prologue)