The Bardo Thodol — known in English as The Tibetan Book of the Dead — is a genuine historical text within the Tibetan Buddhist tradition, composed in the eighth century CE. Its Tibetan title translates more literally as "Liberation Through Hearing During the Intermediate State," and its content is precisely what that title suggests: detailed, practical instruction for navigating the bardo — the intermediate state between death and rebirth.
Instruction, not metaphor
What distinguishes the Bardo Thodol from purely symbolic religious literature is its register. The text describes stages of consciousness separating from the body, and what a person might experience during that process, in the practical, sequential language of a manual — written to be read aloud to someone during the process of dying, or studied in advance as preparation. Within its own tradition, it was never intended as metaphor.
A text older than most Western frameworks for the same territory
The Bardo Thodol predates, by many centuries, most Western frameworks that attempt to describe out-of-body or near-death experience in clinical or parapsychological terms. That doesn't make its claims scientifically verified — it's a religious and contemplative text, not a peer-reviewed study — but it does make it a genuinely significant historical data point: a detailed, internally consistent account of this specific territory, developed independently of and long before modern consciousness research.