I'm not sure why CBS would do the book if it did not have some legitimacy in canon
CBS didn't "do the book", they licensed it out to becker&mayer and 47North. It is no more "legitimate" than books put out by Ballantine, Corgi, Bantam, Pocket/Gallery, Abrams Publishing or Running Press, etc.
King Daniel wrote:
He had no idea whatsoever, thinking the Titan novels and Countdown comic were canon but Destiny and the stuff about Janeway dying wasn't. I was listening and thinking, "For gods' sake man, Google it!"
Canon [for the the purposes of his videogame project].