I prefer to ask the question in a different way, not as a means of disproving the existence or otherwise of god, but of assessing how plausible the claims are for particular "revelations". Question 1 might be: what are the characteristics we might reasonably expect of a work which had been dictated by the Supreme Being? Any number of answers here: precisely worded predictions of the future, i.e. verifiable prophecies, for one. But that's the magic stuff. One of the main attributes of such a work that I would expect is clarity in the explanation of God's plan for us and His requirements of us in matters of behaviour and belief. Don't you think the (frequently violent) disputes over fundamental features of the faith among the myriad Christian sects could have been avoided if God had chosen to be less ambiguous, or (perhaps) more careful in His choice of amanuenses?
Or the Koran. Let's take the Sunni/Shi'a split. The "perfect word of God" leaves no doubt who's speaking on His behalf, but is strangely silent on the leadership of the Ummah after the prophet's death.
So NT and Koran have failed my test. The "revelation" is that they're works of human manufacture and invention. I'm welcome to hear suggestions from other believers who think that their holy writs may stand up better. (No, no, not the Book of Mormon, Dianetics or the collected works of Mary Baker Eddy!)