For everything else, there are rules, rituals, customs readied by the Church.The book takes you on a journey, from the Tibetan perspective, past death, to the journey, according to them, each of us is to take after our lives here.
The moment of death, of separation is a moment one would be willing to lower their self-imposed stance to ideas of other religions than Christianity and search into "other beliefs". It is in human nature to explore the unknown.
Once the book is published, it will have a circulation. Eventually the book meets its readers and by choice they read the book.
Then it becomes a go-to book for explanations outside common beliefs on death and dying.
To read it would not imply studying Mādhyamika. It appears as light reading, yet "transformative" and explanatory.
So that is how it happens: someone who read it introduces you to it.
It can have competition from the Kali cult. A typical motivation will be: "I prefer the human, don't expose me to gods!" because the church does not allow gods, idols. It's not only the content but the context playing a part as well.
There is "The Christian Book of the Dead What do Catholics believe about the fate of the soul after death?" to give answers, but the first book already hit a spot. So that's why is popular: it caught the clergy (East and West) off the guard.
As you see, there are many books. If I were to sell one to you, which would you prefer?The central character in this story is Walter Evans-Wentz (1878-1965), an eccentric scholar and spiritual seeker from Trenton, New Jersey, who, despite not knowing the Tibetan language and never visiting the country, crafted and named The Tibetan Book of the Dead. In fact, Lopez argues, Evans-Wentz's book is much more American than Tibetan, owing a greater debt to Theosophy and Madame Blavatsky than to the lamas of the Land of Snows. Indeed, Lopez suggests that the book's perennial appeal stems not only from its origins in magical and mysterious Tibet, but also from the way Evans-Wentz translated the text into the language of a very American spirituality.