Well part of the problem is that its not one story, like Lord of the Rings, its many - some unique, others like the Flood, ripped off whole cloth from other myths in that area. They conflict with each other in critical parts, which does not help the credibility deal much. Given 4 gospels you have two differing accounts of the last words of Jesus.
Moreover, some of the writers are mindblowing, almost beyond measure. The account of creation is near perfect in its sublime telling. However other parts were law, and written like it (boring). And other parts are not as well written, and kind of yeech. You have the gospel of John, as magical as any Gandalf stuff, and letters of Paul as mean as anything you'll ever read.