The narrative hook of Anderson's work is the friendship between Lia and Cassie.  Part of Anderson's strength in detailing this is that she throws the reader in the middle of their friendship.  This has the effect of challenging the reader to piece together their friendship and understand its development.  The opening sentence in which both are sitting at a coffee shop and talking about the condition in which they are both immersed is one example of this narrative hook being able to challenge the reader and prolong their interest.  Anderson's narrative hook enables the reader to understand the importance of their friendship, but also grasp the level and challenge that faces both of them.  It is this hook that sustains the narrative interest of the reader.  In contrast to typical Young Adult Literature that might have a tendency to display friendship as triumphing over all and friendship between girls as being eternal and almost one dimensional, the opening conversation between both girls ends up demonstrating to the reader the challenges in Cassie and Lia's friendship.  It also goes very far in demonstrating how the reader has to continue to follow their narratives both separately and together in order to better understand each character as well as critically examine the reader's own reaction if they were placed in a similar context.  It is here where I believe that the greatest effect of the narrative hook to Wintergirls can be felt.