While reading my book today, I found one line that stuck out to me. Hannah was talking to Courtney in the tape and she said, "I don't think you do this intentially, Courtney. And that's why I put you on these tapes. To let you know that what you do affects others. More specifically, it affected me." At this point in the book, Hannah is talking about how Courtney uses people, and used her, for popularity to be the 'Most Popular Senior'.
  In the book, it swtiches back between Hannah's words and Clay's thoughts, while he pauses the video. In this part of the book, Clay thinks to himself, "'Courtney does come off as genuiely sweet. Hearing her story here, on these tapes, must have killed her.' A shiver crawls up my back. 'Killed her.' A phrase I will now drop from my vocabulary."
  This quote is very important because it shows how everyone's actions effected Hannah's death. Clay barely knew her, but still even he can't talk about her suicide without shivering.