the books are EU canon (which isnt considered completely original trilogy canon)
only the original zahn trilogy is 100% canon, they have a list of cannon and fuck off books, the entire vong series is canon as lucasfilm used it to jumpstart the failing book sales and create a new basis for all novels written after that

all the republic commando books/games are canon, the dark forces stuff is canon, the new game coming out is also canon, the RTS games arent however as I recall