Guilt and blame. That's what's up with the title. Thirteen Reasons Why points to the thirteen incidents that Hannah says are most to blame for her death. Each of these incidents features one of the twelve people who receive her audio-taped suicide note.
Just because Hannah's last words are neatly divided among the thirteen chapters doesn't mean there's anything neat and tidy about her explanation for killing herself. She's recording on the very last day of her life. She's desperate with her own guilty feelings and with the anger she feels toward the people on the tapes. Most of all, she's extremely confused. The thirteen reasons are more of an organizing principle she uses to try to make sense out of the chaos she feels her life has become.
So we can't be sure if there really are the thirteen reasons why. And neither can Clay. At first, he thinks things like, "These tapes shouldn't be here. Not with me. It has to be a mistake" (3.36). He's sure he never did anything to harm Hannah. And when his tape comes along, Hannah flat out tells him, "Clay, honey, your name does not belong on this list" (11.75).
But by the end of the tapes, Clay feels like he does belong on the list, because he held back from her. And even though Hannah says he shouldn't be on the list, he is on it. Does she or doesn't she blame him? Could he have saved her? It's enough to give us a brain freeze. Clay, too – that's why his head is throbbing throughout the novel. And Clay's tape isn't the only story with major brain-pain potential. Check out the "Characters" section for more.
Now here's something less complicated: the history of the title. Asher says it started with a pun on Hannah's last name, Baker. A "baker's dozen" is thirteen, so a girl named Baker should tell a baker's dozen of stories. He originally titled the book, Baker's Dozen: The Autobiography of Hannah Baker. Cute, but it just doesn't have the same ominous ring as Thirteen Reasons Why. We see the thirteen and can't help but think about bad luck. This title, we would say, is effective in preparing us to read something just as dark and scary.
One last note. The original cover of the book shows the title like this: TH1RTEEN R3ASONS WHY – all caps, with numbers replacing two of the letters. Throughout this learning guide, we've just written it as Thirteen Reasons Why; it's usually referred to like this anyway, plus, it's way less creepy. But we're all about full disclosure.