The Tibetan Book of the Dead

The Bardo Thodol (Tibetan: bardo "liminality"; thodol as "liberation", Liberation through Hearing in the Intermediate State, is a funerary text that describes, and intends to guide one through, the experiences of the consciousness after death during the interval known as bardo between death and rebirth. It also includes chapters on the signs of death and rituals to undertake when death is closing in or has taken place.
It is the most internationally famous and widespread work of Tibetan Nyingma literature.
The Bardo Thodol is recited by lamas over a dying or recently deceased person, or sometimes over an effigy of the deceased. This a sign of the influence of shamanism on Tibetan Buddhism[citation needed]. The name means literally "liberation through hearing in the intermediate state".
The Bardo Thodol actually differentiates the intermediate states between lives into three bardos (themselves further subdivided):

the chikhai bardo or "bardo of the moment of death"
the chonyid bardo or "bardo of the experiencing of reality"
the sidpa bardo or "bardo of rebirth".
The chikhai bardo features the experience of the "clear light of reality", or at least the nearest approximation to it of which one is spiritually capable.

The chonyid bardo features the experience of visions of various Buddha forms (or, again, the nearest approximations of which one is capable).
The sidpa bardo features karmically impelled hallucinations which eventually result in rebirth. (Typically imagery of men and women passionately entwined.)
One can compare the descriptions of the Bardo Thodol with accounts of certain "out of the body" near-death experiences described by people who have nearly died in accidents or on the operating table - these typically contain accounts of a "white light", experienced as, somehow, a living being, and of helpful figures corresponding to that person's religious tradition.

The Bardo Thodol also mentions three other bardos: those of "life" (or ordinary waking consciousness), of "dhyana" (meditation), and of "dream". Thus together the "six bardos" form a classification of states of consciousness into six broad types, and any state of consciousness forms a type of "intermediate state" - intermediate between other states of consciousness. Indeed, one can consider any momentary state of consciousness a bardo, since it lies between our past and future existences; it provides us with the opportunity to experience reality, which is always present but obscured by the projections and confusions due to our previous unskillful actions.
According to Tibetan tradition, the Bardo Thodol was composed by Padmasambhava, written down by his primary student, Yeshe Tsogyal, buried in the Gampo hills in central Tibet and subsequently discovered by a Tibetan terton, Karma Lingpa.