Once in a while a really well written story can feel so real that you begin to wonder if it might not be based on a true story. Occasionally this is actually the case, or supposedly so, but there are times when an author (etc) will go right out of their way to create greater immersion in their work by claiming that their very obviously fictional and fantastic world is in some way real. Usually they claim that they didn't come up with the story, rather it was recounted to them by the actual main characters (or some other witness), often physically, but sometimes by phone or magic. Other times they will claim that they found the account in the form of a diary and novelised it, or, if it is a film, that it is comprised of found footage or a mixture of found footage and Dramatisation.