It's no accident that Hannah addresses Clay as Romeo at the beginning of his tape, quoting directly from Shakespeare's Romeo and Juliet.
Hannah can relate to the teenage Juliet, who takes her own life rather than live unhappily. Luckily Clay doesn't relate to Romeo, who accompanies his sweetheart into the great beyond. In this way, Thirteen Reasons Why subtly suggests that Romeo and Juliet romanticizes suicide by connecting it with the idea of true love. Jay Asher certainly has no intention of making suicide seem anything but grim and tragic.
But wait: Juliet commits suicide because she can't be with her one true love. If this is the case, did Clay have more to do with Hannah's death than we originally thought? Not necessarily. Living without love sounds a lot like what Hannah is going through regardless of her relationship with Clay: she doesn't seem to be getting any love from family or friends, or even mentors.