Not all sacred text are allegorical. The Tibetan book of the dead is a handbook for the departing soul giving expicit instructions for easing the passing from this life to the next. It was intended to be read aloud by those who watch over the dead on 49 successive days - being the period the soul is beleived to linger in the bardo, the intermediate state between death and rebirth.
though it was written moer than a thousand years ago, its decription of the three phases of death is strikingly similar to modern accounts of NDE's, although there is no mention of a celestial paradise because the Tibetans beleive that the bardo is a state of mind in which discarnate conciousness creates its enviroment according to expectations.