...it might also be noteworthy to suggest that very few religious texts stand on a firm authorship ground (unless we are discussing L Ron Hubbard). Most of the Torah was written down well past the time of Moses. Genesis in particular has two creation stories, and also some weird subtexts that are seemingly along the lines of greek type mythology.

The Quran might seem less susceptible to redaction, but its authorship is not particularly well established. With Mohamed being supposedly illiterate, it's unlikely he wrote the text. More likely that his followers wrote it down sometime during and/or after his death. Though there seems to be some thought that the authorship was purely divine - which means that its basically unknowable - we know its Gods word because God wrote it type of reasoning.

You'd probably find similar problems with the Hindu and the Buddhist texts as well - supposing one were inclined to a methodical objective analysis. But such literary analysis problems aren't likely to phase the believers, since leaving the question open usually lends a certain quality of mysticism - something that never seems to hurt in that line of business.

If you are a believer in one of the historical based religions (Christianity, Judaica, Islam, etc...), then I'd think that you'd have to admit that God mostly acts through man. And anytime you enter man into the equation, you pretty well have skewed history very much on the side of imperfection.