If the question is to establish facts from the book, the most elemental ones would be that the book is told through the lens of two people.  One of them, Michael, is responsible for the death of Jenna's father.  From this, the novel delves into the issues of responsibility and guilt.  The other facts that come from this would be how the work probes into the perception of one who commits crime and the survivor who must deal with the consequences of it.  Another fact from the book is that there is the issue of gun control raised from reading it.  This fact helps to drive the perception of the work.  One can believe from this fact that the presence of guns needs to be reduced or that individuals need to be punished when they fail to handle guns properly.  Finally, I think that another fact that comes from the novel is how individuals end up wrestling with morally ambiguous issues.  Jenna's struggle with vengeance as well as the pain of how to deal with death and her responsibility within it is another fact that arises from the novel.  At the same time, Michael is forced to come to terms with his own actions, recognizing that the desire to want to escape punishment and responsibility might be just as bad as enduring the punishment for mistakes.