afaik the "Tales from the Paranet" (that was the title iirc) will also include some stuff about the farther reaches of the nevernever
Do you have a source?
I believe this interview has more information on the supplement, so check it out: http://www.thewalkingeye.com/?p=973
Basically, some updates on how to use stuff from the most recent books, and a whole lot of city creation examples. The city creation examples aren't canon (and neither is Baltimore, as far as I know), just things to give people ideas. Among the "cities" that are planned for the supplement are the Nevernever, the entire continent of south america, a traveling game, and a Florida swamp town.
He's the way I view Canon, since the RPG is supposed to be "canon" in Dresden's world- the comments Dresden makes in the margin are theoretically canon (example: In RPG
Your Story 364, Bob talks about Gilgamesh- see below). However, most of Baltimore is hypothetical canon- the "author"- Alpha Davian Campbell (another theoretical canon, since he's writing in-universe for the RPG- says he makes up some of it.)
My interpretation of canon:
1:Jim Canon- A Novel, Short Story, WoJ. This comes from highest authority, and cannot be contradicted (occasionally retconned by Jim)
2:Theoretical Canon- ex: Davian Campbell, Gilgamesh. From a supplement, like the RPG, where it is written "in-universe" and canon characters comment about the material outside the RPG. (example: Bob talks about Gilgamesh in the margins such that he is canonically a Accords signatory). WoJ/later novels can contradict, but should currently be taken as legitimate.
3:Hypothetical Canon:- Damocles Ravenborn, <most of Baltimore material>- Possible but not confirmed canon from a supplement. It is never directly stated as factual or fictional. WoJ/later works can affirm/deny (example: Baltimore chapter of YS- in-universe author Davian Campbell states he makes up some of the material, and some of it is factual). Unlike Davian Campbell, who gets a affirming mention from Harry, Bob, or Billy, these entries have no reason to be canon or non-canon.
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4:Parallel Fanon: An unofficial work- usually by fans- of the Dresden Files, not associated legally, etc. It may be an RPG campaign, short story, etc. However, it does not contradict present canon at the time of its inception (later canon from above could bump this down to 5, see below)
5:Contradictory Fanon: An unofficial work, as Parallel Fanon. However, this work contains some contradiction with present canon, and could not co-exist with Butcher's precise universe.