Let's suppose, for the sake of argument, that every person who wrote a book of the bible wrote it as a complete work of fiction. With Genesis, that's an easy sell. But people took these books, originally written as fiction in order to spoof or fool other people, and assumed they were real truthful additions to the collection of holy texts. The more people took them seriously, the more people wrote 'spoofs' of those books, which in turn got taken seriously. We need not know the reasons why exactly, because people write satires and fan fiction and forgeries all the time. It's not impossible that the author of every book of the bible self-consciously knew it to be untrue, a work of fiction, and only later was it taken to be true by the Jews and Christians.
So we have a real possibility that all the books of the bible are fictional, and that them being fiction is their correct interpretation. My question to you Drich, is how do you know that this is not the proper interpretation?
(And I'll stress the word 'know' — how do you know this is not the case, not simply that you believe it isn't the case. After all, what you're asking of us in return is quite substantial; a mere 'whim' of belief won't cut it.)