To start with, it seems that the existence of God is, a priori, slightly less likely than His non-existence by Occam's razor as the non-existence assumption requires one fewer agent to be postulated.
Having taken this into account the Bible seems to me to be as one would expect from an omnipotent, omniscient deity: as a revelation it is not exactly how we would like it but surely we'd expect our desires to be at odds with God's plan for the universe? Different parts of it have meant different things to different people at different times which is either a sign that the Author is incredibly clever (some poetry seems also to have this property - that you can get different things out of it depending on your situation when you read it: if God were an omniscient poet then he could arrange things so that different people could get different things out of the same reading and for it all to be for the best) or a sign that humans are not particularly good at the listening/reading part of communication - or both. The revelation of God seems to develop during the Bible which is consistent with a document that has been revealed in chunks to a group of people over a period of generations. I can't see that we need postulate any more than the existence of God for this theory to hold water.
The alternative theory starts holding the advantage - no deity to postulate. Religion, for one reason or another, comes naturally to humans - different tribes have their own take on it but the belief that there must be someone out there to blame for the universe seems central to our species. There is, however, a question of why this is. If there is a God then belief that there is a god is already explained. If there is no god then why do so many humans believe in one? There are a number of possibilities but they all involve a bit of postulating. Maintaining an oral history of the tribe and interpreting it in terms of the gods of the tribe seems natural, as does writing it down. When something is written down after generations of fireside story-telling it is possible that there will be exagerations, that history will have turned into legend and fairy story, that odd events will have turned into miracles. The Old Testament, I think, is quite consistent with the "no god" hypothesis. The New Testament is a little more complicated. The tribe is now settled, writing is common, they are in contact with well documented nations. The stories are not the results of generations of oral tradition, they are written as eye-witness accounts by contemporaries of the Jesus character. There are a few possibilities. Possibility 1) It's true but not evidence of the existence of God - this is very tricky, the resurrection of a crucified person requires quite some explanation. Maybe there was a secret cult that arranged a pretend crucifixion, maybe the Romans didn't do a very good job, maybe current medical understanding of death is flawed. None of these are very satisfactory to my mind. Possibility 2) it's the result of hysteria. Jesus was a very charismatic preacher, the disciples were caught up in his dream and when he was killed they went a little mad, told each other that he had said that he'd rise again, told each other that they saw him and went out into the world to tell everyone of what they thought they had seen. Possible, but it does require that we believe in the power of this hysteria. Possibility 3) it's all lies. Paul, Peter, John, Matthew, Mark, Luke, James, Jude, The writer of the Hebrews and several other people either cooked up a set of lies for self aggrandisement or went along with what they knew were someone else's lies. Again, possible, but they didn't get much by way of wealth and fame out of it. There would have been some glory from the leadership of a cult but it was glory that ended for most of them in death by torture. Possible, but not, I think, convincing. Possibility 4) I'm all out of possibilities, sorry.
The "No God" assumption can be made to hold water but it requires some postulation about the behaviour of people that I think removes the Occam's razor advantage previously held. Which story do you believe?