Please answer the following question: Dark Matter (Zeh novel) - Dark Matter (German: Schilf) is a 2007 novel by the German writer Juli Zeh. It was published as In Free Fall in the United States. It tells the story of a physics professor who is told he has to kill a man in order to get his kidnapped son back and a detective Schilf who steps in to solve the case. As of December 2011 a German film adaptation directed by Claudia Lehmann was in post-production. Given a choice of categories company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work, the text refers to which one?
A:
Written Work