sry for going offtopc now ;)
It's written by Orci and Kurtzman and distributed as official prequel to the movie.
So it's not "canon" in the original way, but it's the very first "official" book/graphc-novel out there.
Alot of "canon" things aren't making sense or are contradictorily. But the events stated in "Countdown" do make sense.
sry, again. back to topic now xD
-Edit: Okay, I'm sorry. I just read an interview where Orci stated that he wanted it to be canon but rather leaves those events to fan-fiction.
Still, I think the "Narada" shown in "Countdown" should be created by someone. Maybe I'll do it. ;)