Astral Stuff

I am not sure what to make of the concept of astral travel. I have read in Tyson's works that anything that happens in the astral plane happens in the mind alone and not outside of the mind. If so, what is the difference between astral travel and reading a good book? To me, it seems silly to imagine an unseen place without a good script, as found in a good book.

Also, what is the difference between astral travel, as defined by Tyson, and writing fiction?