Oh, I forgot to add:

My personal *favorite* thing (since there is no real timeline) here would be to find someone who's willing to sit down and read through the book itself, and get an idea of the world and take notes for the map in that way, to make sure it's as accurate to the text of the book as possible. But I also *entirely* understand that that's a nonstandard thing, and no one has an interest for that, and will do everything I can to work with you and convey all of the relevant information from the book as best I can.