Personally, I would chalk it up to a dream, but that is just my opinion.
I have had the most vivid dreams that were so real I couldn't believe they weren't reality.
I haven't even heard of the book.
We just have no idea what is true; others have claimed to have visited hell.
Whether they truly did or it was a dream, we can't know if it was God or not, wanting the person to have the experience.
I would much rather have a dream of what heaven is like but then maybe that is just too awesome for a human being to comprehend~who knows?