Well, in point of fact, CBS was very involved in the production of the book - the manuscript had to be approved chapter by chapter by the head of licensing of CBS inc.
Not disagreeing with you, but CBS didn't "do the book", as the OP (Enterpriserules
) insisted. CBS 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, or any other licensed Star Trek tie-in.
said: "I'm not sure why CBS would do the book if it did not have some legitimacy in canon..."