Why do many Biblical books have the earmarks of fiction?

For example, private conversations are often related when no reporters were present (i.e. conversations between God and various individuals are recorded--prehistoric events are given in great details) When a story is told by more than one author, there're usually significant differences of how the story has been told. Many stories--stories in original context are considered by many Christians to be fictional--were borrowed by Biblical authors, adapted for their own purposes, given historical settings, and then declared to be factual.