Despite the party line from Disney and the Story Group, I'd be hesitant to treat a lot of the material released in the pre-TFA build-up as 100% hard canon, given how many errors and inconsistencies with TFA pop up, like the Finn centred YA novel getting his backstory completely wrong with what was established about him in TFA.
If you're referring to
Before the Awakening, I read it. I have a copy of it. It's in line with the movie. (In fact, it was used as backstory in the movie's junior novelization, which is also considered canon -- albeit a little more squishy in continuity due to the realities of novelizing movies before the final cut is finished).
In any franchise, errors will pop up, due to accidents, the realities of trying to create interlocking materials in a franchise were new stuff is being produced at the same time. It has happened before in the
Star Wars franchise and it will happene again. But, we have plenty of examples in
Star Trek of mistakes and errors in specific episodes and movies, and we're not debating if those installments are canon like the people who created them told us they are.
And in the case of the
Star Wars Story Group material, we're getting unprecedented levels of corroboration across media (like Episode 8 director Rian Johnson contributing to the storyline of the Episode 7 prequel novel
Bloodlines,
Force Awakens backstory being seeded into the Dark Times-era young adult book series
Servants of the Empire, which also overlapped with a TV crossover in
Star Wars: Rebels). I've also listened to podcasts interviewing writers for the Story Group, who've gone one record that they're seeding stuff in media today for future projects and stories years down the road. So, until the time that Disney chooses to create another reboot, I think we can safely say that
Star Wars is going canon across everything and it's here to stay, because so far, they've delivered.