I remember reading that someone who worked on the early TNG said that Roddenberry said that TOS was "not cannon." He clearly didn't meant that it was ignored completely (obviously since Bones is in the first episode and the second one references the TOS story that it rehashes), so I take it he meant that they could just choose to ignore certain stories or details if they decided too. That's the way the show always worked. He also said that the only TAS story that was cannon was Yesteryear.
I guess the fifth movie is referenced in novels and in the Star Trek Online game, if that means anything to you. I've never read any of the books.