Divinely Inspired Iron Age Morals?

If a book really was inspired by an all-knowing, perfect god, how would we go about finding out? After all, several books from different religions make this claim, but how do we determine which of them, if any, actually live up to it?

In the case of the Bible, we know the individual books were literally written by humans. The only question we need to answer is about where they got their information from. Did a god really tell them what to write? or did their words have a rather more human origin?