A couple months ago I read Raymond Moody's book Paranormal-My Life in Pursuit of the Afterlife. I had to go back and check but the story you mentioned above about the soldier Er in Plato's Republic is the same story that Raymond Moody discusses in Chapter 4 of his book. He talks about his experience reading Plato's Republic at University and how he was swept away by it. The story about the soldier Er would be the story to kindle his interest in studying the afterlife.While making my way through Plato's Republic I came across an anecdoate that Plato relates to us through Socrates at the end, and it is a description of the afterlife, rewards and punishments proportionate to the virtues and sins, karma, the reincarnation of both humans and animals, and the source of incarnational amnesia.
I almost fell out of my chair when I read this. In my decade-long love of philosophy not once did I ever actually come across even a mention of this anecdote or story, in spite of the fact that I've heard countless times people mindlessly repeating Plato's tale of the Cave --- and both the afterlife and this cave analogy are from the same work!!! It just goes to show you how important is to read primary sources. Jee-zus!!
From Chapter 4:
There was another thing that drew me to Socrates, and that was the fearless way in which he wrestled with mankind's most important question: What happens when we die?
At this point in my young life, my interest in the question of an afterlife was like my interest in studying black holes in astronomy: though many astronomers believed that black holes exist somewhere out there in the vast universe, they had been unable to prove that black holes exist or describe how they work. I felt that the question of the afterlife was the black hole of the personal universe: something for which substantial proof of existence had been offered but which had not yet been explored in the proper way by scientists and philosophers.
Socrates was doing that very thing in The Republic. Everybody knows that The Republic is about justice. But at its heart it is really about justice and what justice is in relation to life after death. At the very beginning, Cephalus brings up the notion of life after death, which frames the entire work in the notion that justice is related to the afterlife.
But it was the story told about the soldier Ur by Socrates at the end of Plato's Republic that truly kindled my interest in answering questions about the afterlife...