If an ego-maniacal m murderer wrote a book saying how nice he was would we believe him?

All through recorded history different peoples have believed in a God or Gods and have visualized them in different ways. That doesn't mean that there is no God. Some Gods have been lecherous (as the Greek and Roman Gods) and early in the Old Testament God was seen to be vengeful, even to the innocent children of sinners. The prophets gradually improved the image of the Judeo Christian God and His image reached its peak in the teachings of Jesus of Nazareth. If there is a God (I am agnostic) perhaps He revealed Him/Herself to people of the time in ways that they would expect and understand.