"Gospel, or canon as we refer to it, includes the screenplays, the films, the radio dramas and the novelizations. These works spin out of George Lucas' original stories, the rest are written by other writers. However, between us, we've read everything, and much of it is taken into account in the overall continuity. The entire catalog of published works comprises a vast history — with many off-shoots, variations and tangents — like any other well-developed mythology."
Quit confusing canon and continuity, and quit getting all of your information from wikipedia.