Well, regardless of the other comments I think they should be made canon. I could care less about TOS, im speaking in terms of post show and in-between movie. The books are not being churned out factory-style like in the past and it would not be hard to keep them consistent. They have already started doing this with the books. But whatever. Its my opinion.
Being consistent and being canonical are two entirely unrelated concepts. Canon means either a) the core body of work as distinct from adaptations and tie-ins or b) the current producers' working assumption about the history and continuity of the franchise. Neither of those has any applicability to the books published by Pocket or the decisions of the editors making them. The editors can certainly choose to make the books mutually consistent, and they usually do. But that has nothing to do with canon.
Say J.J. Abrams did decide to declare certain books canonical. What effect would that have? It wouldn't change their contents. It wouldn't make them more enjoyable works of literature. And whoever takes over the running of the franchise from Abrams could declare that those books are apocryphal. Or Abrams himself could disregard them if he had a movie idea that required doing so. One of the many, many things that canon does
not mean is "binding on every subsequent creator forevermore." Creators ignore their own or their predecessors' definitions of canon all the time.
Dallas decanonized an entire season of itself.
For a perfect illustration of what a useless bit of nonsense "book canon" is, look at the
Star Wars Expanded Universe. Lucasfilm's licensing department claims that all SW books and comics are canonical, despite the fact that many of them contradicted the hell out of each other well before that decision was made, and that many of them have been contradicted by subsequent movies. So they've had to fudge it by making up some convoluted stuff about "levels of canon," so that some stories are more "real" than others. And then Lucas comes along and makes the
Clone Wars TV shows and blithely ignores what the allegedly canonical books have declared about the Clone Wars. Not to mention that the current
The Clone Wars 3D-animated series arguably decanonizes its 2D, article-less predecessor.
So declaring the SW books and comics "canon" had exactly zero effect on their relevance to the filmic SW universe. It's just a meaningless sound. Declaring them "zygrex" would be just as useful. The only thing it means in practical terms is that the creators of SW tie-in fiction try to be consistent with each other's works as well as with filmed canon. And since that's mandatory for them, it creates all sorts of complications and convolutions as they try to reconcile all the inconsistencies and pretend it all fits together. In ST fiction, we have the freedom to make consistency optional, which gives us a lot more creative leeway, if you ask me.