I am The Messenger: Markus Zusak

Zusak's books are always original. I believe this is a teen book... In this one the protagonist gets a task from someone he doesn't know to see certain people. The message is given on a playing card. He studies the people and has to determine what they need. After he completes what he thinks he is supposed to do for the people, he is given another card and works his way through the deck. The tasks range from beating people up to keeping them company. His actions always help someone in the end. What he believes to be the last 2 cards help two of his friends, the last card is for him. The ending was sort of odd where you can't be sure the person sending the cards is actually human. The messenger becomes the message that everyone and anyone can do something for another that will improve their life. It ended with a "play it forward message"