I prefer to work around or against. When using predetermined settings, the problem with trying to stick to canon is that PCs can and will do things to completely disrupt any existing notions. There's also the fact that I am not omniscient, so I'm bound to forget things, make mistakes, and screw up the canon on my own.

I'm going to be running a Star Wars campaign soon. It's set in the Republic Era, because I'm only really familiar with that and the Rise of the Empire from the movies. Our group's other GM has set games in the Old Republic, but my interest in the setting really begins and ends with the movies.

However, I KNOW the players are going to disrupt things. They'll be following a parallel story to episodes IV to VI. I've flat out stated: "You can affect events from the movie. You can change the course of history. You can end up killing Vader yourselves - but don't count on it." I guess that's an example of working against canon.

As for working around it, I have an idea for a "Legacies" Justice League game, where it's set 50 years or so in the future. The original League is retired, dead, lost, or otherwise out of the picture. In fact, most current heroes are (though there are a few still hanging around). The PCs would be the new Justice League, each taking over the role of a previous member, but not necessarily in the same way. The Superman analogue could be a guy in a powersuit, for instance. The Batman analogue could be an actual metahuman with bat powers. And so on.