The canon, according to Lucasfilm at the time they established it, is:
The movies
The clone wars CGI movie
The six season Clone Wars TV series
Rebels
Everything else is 'canon' in the sense that it happened unless the movies do something to invalidate them, at which point they are no longer canon.
I'm pretty sure that, at present, Shadows is considered 'canon' in the soft sense, meaning that if they ever wanted to fill in the gap between Episode 5 and 6 with a different story, it would no longer be canon.
But a lot of material has come out talking about the Outrider being the ship of Dash Rendar, and Black Sun is widely recognized in the same sense so I'm pretty sure it still happened in the minds of the current content authors, for whatever that's worth.
I like Shadows of the Empire. One of the few EU things I liked.