I don't really want to get into an argument about precisely what's canon and what's not canon..
Okay. I'd kind of like to pursue this line of discussion a little further, so let me know when you've had enough and I'll stop.
...but consider this: most of these tie-in books -- that is books based directly on or relating to the events of the movie -- were most likely written while the movie was still in production and certainly before it was released. That means in all likelihood all the authors would have to go on for this sort of thing would have been the shooting script.
That would be the case for some of them. (I do remember listening to a podcast interview with one of the authors, I think it was Jason Fry, and he did admit that when they're working on stuff at the same time, some inconsistencies will occur.)
That's great for the major details like names, places and the nuts and bolts of dialog and plot. However it's lousy for interpreting character motivations and internal thought processes.
I've actually found that the novelizations tend to play the fastest and loosest with dialogue. For what its worth, with the TFA novelizations I've seen so far, they're reasonably consistent with the characterization. The stuff that isn't is material in stuff that either outright conflicts with the movie (and so is obviously not canon info), either by not being able to have happened or said (for example, the showdown with the gangs and the rathtars has a lot of extra lines; very few of the extra ones actually happened off-screen.
Names and places I'll grant. I've found that these novelizations tend to get characterizations pretty good (although I will concede that the Foster novelization feels the most off). The majority of problematic scenes don't even mesh with the movie in the first place, so there's no need to insert them in the first place.
Forget what the book says for a moment and just
watch the scene. She's pretty much calmed down until Maz holds out the sabre and then she freaks out all over again.
I guess I assumed that she was not as calm as she looked. Even before I read the books, I did think she still seemed pretty fragile, stressed out over her Force experience, and not in the best state of mind to be looking at her life objectively.
Another reason why it's not a good idea to get too dogmatic about what's in the books when it comes to interpreting the movies is how some of deleted scenes are still present.
For the most part that doesn't harm but enhance, but there are a few that dramatically alter how one interprets a character's mindset.
If a deleted scene made it into one of the novelizations and doesn't conflict with the movie, it would be considered canon (like the adult novelization's extra scene were Rey is waiting outside the operating room at the Resistance base or the bit with Unkar Plutt on Takodana).
To give a specific example: in the novelization the haggling scene between Rey and Unkar Plutt is intact as per the script. But they way they chose to edit that scene alters it's meaning significantly to make Rey seem a lot less mercenary and more loyal to BB-8.
Even the exacts of it are different from version to version:
- The adult novelization has Rey negating when Plutt makes the mistake of annoying her one times too many.
- The junior novelization and
Rey's Survival Guide run with the idea that she realized she was making a moral compromise that she wouldn't be able to live with.
- The
Rey's Story novelization puts it on her having compassion for BB-8. (Incidentally, this version fills in the gap of the movie between Rey and BB-8 arriving in town and her going to Plutt's stand, showing BB-8 starting to worm his way into Rey's heart.)
However, since the scene isn't canonical in the first place (since we saw the scene in "real time" and there's no gap for this to happen), I don't think it's anything more than an interesting "behind the scenes" look at how the movie couldn't been (and shows that, in the movie, Rey was turning down an offer she couldn't afford to refuse in more ways than one).
What I'm saying is that it's best not to take "these books are canon" too literally and take their characterisation with a grain of salt because it's filtered through the author's personal interpretation and what suits the narrative they're weaving with the events.
Short version: it's *a* valid interpretation, it is not *the* valid interpretation.
Officially, everything has equal weight, which is a little overly simplistic. Understandably, I'm sure pretty much everyone assumes that the movies have seniority, with the TV shows next, and then everything else.
Novelizations are a little loosey-goosey in their place in canon, given that the extra information is canonical, even if the way it's presented is not (except when the information is just plain wrong). For example, the novelization's version of Snoke's first scene has extra dialogue not in the movie (nor could it be put back into the movie as having happened off screen) that gives him more backstory. So, while Snoke and Kylo Ren discussing Snoke's background at that moment is non-canon, the basic information there is. (Confused yet?)
Personally, I tend to put novelizations at the bottom of the canon list, since they, by nature, have some discrepancies which need to be ignored, and have historically been treated as optional by other tie-ins. However, until its overwritten, new information in novelizations that meshes is canon, so I guess I don't think it needs quite as much salt as you think.
(This's all IMHO.)