This is a young adult (YA) novel by Jay Asher.
Here is the book description from Amazon.com:
"Clay Jenkins returns home from school to find a mysterious box with his name on it lying on his porch. Inside he discovers 13 cassette tapes recorded by Hannah Baker his classmate and crush who committed suicide two weeks earlier. One tape, Hannah explains that there are thirteen reasons why she decided to end her life. Clay is one of them. If he listens, he'll find out how he made the list. Through Hannah and Clay's dual narratives, debut author Jay Asher weaves an intricate and heartrending story of confusion and desperation that will deeply affect teen readers."
WOW!!! Keep coming back to hear my comments as I read the book. I hope you will consider reading it as well.