The Tibetan Book of the Dead is an ancient text that provides guidance on navigating the journey of death and rebirth. It is a collection of teachings and rituals meant to help the deceased transition into the afterlife. It is believed to have originated in the 8th century and is still used today by Tibetan
From Wikipedia
The Tibetan Book of the Dead: A Liberation Through Hearing is the first opera by American composer Ricky Ian Gordon. The libretto is from Jean-Claude van Itallie's theatrical adaptation of Buddhist teachings, Tibetan Book of the Dead or How Not to Do It Again.