This is going to start out sounding like I'm not talking on subject. Stay with me for a second.
Books and gaming are different media, with different strengths and weaknesses. Creating them serves different needs and has different power dynamics. While there is some overlap in what works well in both, there are times when stuff that's brilliant in one quite simply doesn't work in the other.
An author is trying to tell a story. To do that he needs to create and justify all the actions which comprise that story. We need Harry to get into the Nevernever, so there will happen to be a way to get there; it will generally be dangerous or complicated, but that's all part of the creating a story thing. Here's a key concept: With a book you go back and rewrite stuff, and you need not fully flesh out some aspect of the thing.
Okay, how's this relate to what we're talking about?
Well, games don't quite work that way. For one thing, everyone sitting around the table contributes; the power is more diffused around the group. There's actually a thing in the FATE system which allows players who aren't the GM to say things like, "This gate into the Nevernever is sensitive to blood magic," and be right (if they make their roll, of course). So the story draws from the imaginations of everyone sitting around the table, and it happens in real time; you don't generally get the chance to edit a role playing game.
Now, to draw this a little tighter onto topic.
A lot of the particulars about the Nevernever is likely to be at least somewhat different from the books. As a group, you and the other folks around the table will all contribute aspects to it, and you'll all decide how to use it to make your game more fun. Also, we don't know if the Nevernever in Chicago behaves the same way as it does in, say, Boston.
I guess that basically this was all a rambling way to say that the Nevernever is just a tool to help your gaming group have a good time. Because role playing gaming has different strengths and responds to different pressures, the way you use that tool will be a little different from how Jim uses it in his novels.