He plays with the literal truth and based his fiction on other fiction : which had really happened. He adopts an autobiographic way, presenting himself as a simple editor proof reader of the true documents and describes background details as if they really exist.
His plain language is different from the plain language of others writers. His realism is the principle that joins the different narrative elements and gives artistic coherence to the world of the novel.
Defoe became an expert at over lapping truth and fiction.
(The Fortunes and Misfortunes of the Famous Moll Flanders. Edition by Javier Sanchez Diez. Catedra . Letras Universales. 1999.) (The short Oxford History of English Literature. Andrew Sanders. Clarendon press. Oxford. 1994)