What exactly makes it proof of a god and not just a book of good predictions?
I really don't understand how giving accurate predictions on extremely broad topics somehow is evidence of a spiritual being.
They are predictions written about the most conflict ridden area of the world by human beings who will keep doing what they have always done; look in awe at the wonder that is around us and use god as a simple blanket explanation for everything that has not been properly understood.
There is a verse that says "I tell you these things before they happen, so when they do happen, you may believe." The particular verse escapes me right now, but that's the purpose of prophecy.