Reading the posts in the thread over again, I feel there has been a miscommunication on my part which has lead to a few assumptions. I have never been worried about the RPG books spoiling things, as that has been discussed and accepted (by my understanding, I hate speaking for other people), likewise even if we play a game that has nothing to do with The Dresden Files series itself, I would be fine with that so long as everyone is having fun and enjoying themselves.
My main worry is that, having not read the books, the people in my group wont get some of the more subtle aspects of how the game is meant to reflect the series mechanically. If all else fails and we decide to build our own world, are the mechanics in the game books robust enough for such a game?
Also regarding my prior comments on canon, I am less concerned about any of the events that happened in the book series as I am concerned about some of the background information that isn't covered in the RPG books impacting gameplay somehow. While this is a moot issue if we decide to simply make things up, I would like to at least TRY to have fun in Jim's world.