If George Lucas' words are to be believed/followed, nothing outside the movies is direct canon.Mr. Omega said:Well, it's easy to see which part he had the most fun writing... it certainly was the most fun part to listen to. Mario = Superman. Yes.
Also, good job explaining a big reason why I prefer Marvel over DC in less than a minute.
Also, regarding the SWEU: assuming no movies come out before the prequels, what happens to the books set then? Are they considered part of the canon or is the EU an all-or-nothing affair?