from Hal Taussig A New New Testament:
The assumption that the existing New Testament was always the privileged, authorized book about Jesus is not true. The New Testament did not somehow descend from God after Jesus was gone. Christian churches spent centuries engaging in arguments and political deals to decide which early books would be included in their most sacred collections. This, of course, does not mean that the New Testament is fraudulent or less meaningful. It simply means that the historical record shows that collection to be a product of complex human negotiation over a long period of time.
For instance, none of the traditional New Testament was written after 175 CE; so the 2012 council that chose the new books also did not allow books definitely written after 17S CE. Although there is little certainty about when, by whom, and for what these individual-works-were-written there-are some general similarities in all of them. They were all – traditional and new-composed by and for people between 50 and 175 CE, somewhere around the Mediterranean Sea, with certain similar themes and within certain realities of life. All these books had a life of their own long before they were in the New Testament-not unlike the new books added to this new New Testament.