You can create a taxonomy of fantasy based on the operational closure of the setting. I'm writing this on my phone so I'll be brief.
Operational closure means how self-contained the setting is.
The first taxon is the thread that goes Tolkien-Eddings-Martin. Here, the setting is an entirely operationally closed one. It purports to be self-contained entirely, and moreover to abide by internally consistent metaphysics and tone. Its paradigm RPG setting is the Pathfinder one.
The second taxon is the thread that goes Vance-Wolfe-Harrison. The setting is physically operationally closed (it is self-contained in the sense that it is independent of any other reality) but not metaphysically so. It exists in counterpose or contradistinction or ironic juxtaposition to our own reality.
The third taxon is the thread that goes Machen-Ende-Holdstock. The setting is operationally open. It assumes the existence of another reality (our own) and the story is based upon the interactions between those two realities.
I am going to end this brief post by saying that as I get older I rank these three approaches in reverse order. The most difficult but important fantasy stories are I think in taxon three. The easiest but least important are in taxon one. This is in direct opposition to how I would have ranked the different approaches at age 18.