I'm at the DC Rebirth retailer road show

I think they had the same rules with the previous (pre-Episode VII) canon? All comics, games, novels, etc. had to be approved by Lucasfilm's continuity guards, and they were all considered canon... And then what happened was that, once The Force Awakens was in the works, obviously a lot of the old canon would have to be abandoned (since it depicted post-Episode VI events in ways that would contradict with Episode VII), so they decided that all of the old canon except for the movies + the Clone Wars TV series was now set in an alternate universe. I think the old canon is now called "Star Wars Legends" or something.

AFAIK Star Wars has been pretty unique in this regard that they've tried to include all stories in different media into the canon, so that the timeline of their universe includes all that material, and different stories shouldn't contradict each other. With Star Trek, for example, only the TV series and the movies are considered to be official canon, everything else is non-canonical.

IIRC there were levels of canon, so the book level was canon unless it was contradicted by the films, the comics were canon unless it was contradicted by the books or the film, and so on.

I like earlnash's point about the Star Wars books being "old school Marvel" - i.e. mild continuity, one author just getting on with it for several years, each new story really *is* a potential starting point for new readers, etc

i.e. the days before continuity was a beartrap and american otaku and children were the key demographics