Been thinking about the different vehicles for Alternative (or if you’re American, “Alternate”) Realities in literature and related media forms. The list I came up with isn’t as large as I thought it would be and I’ve duplicated several times in my mapping. I’ll post the results at a later date when I’ve given it sufficient thought.
Edit: I was also thinking wider than just a multitude of universes and into altered states of consciousness etc. or the creation of alternate worlds e.g. Myst.