Would it be a letdown if you discovered that your near-death experience of an Afterlife turned out to just be a dream? That what you took to be an Afterlife isn't real and that the experience was something like a hallucination? You might be surprised to learn that Fischer argues that the unreality of the Afterlife in no way diminishes the significance of near-death experiences for those who are sincere about them. He argues that near-death experiences can provide us with emotional understanding (which is quite different from cognitive understanding) that is quite similar to how we understand narratives in fiction. Fictional narratives are no less meaningful in virtue of being fictional and so too with dreams, hallucinogenic drug trips, and near-death experiences. 

Fischer's argument here in chapter 9 is premised upon the success of his argument from chapter 8 (that near-death experience offer no evidence whatsoever of the existence of an Afterlife), but were that argument to fail, then so too would his argument struggle in chapter 9 as well. If the evidence near-death experiences give us of the existence of an Afterlife turns out to be misleading, because there would be no such place, then so too would one's experience of it be a letdown: it's significance and meaning would diminish for us. Do you remember what it was like to discover that the Tooth Fairy or Santa Claus wasn't real? It was a letdown and for some of us a big letdown. So too is this the case with near-death experiences and the Afterlife.