Except that Glen created them after he handed the series over to the screen writers. Considering that Glen never had KARR invented in the first place, that KITT was the only and first one, then him turning around and turning it into a novel was hypocritical. As has been stated before, when it comes to canon, what we see on the screen is what we get, and what we deal with.
But if you want to blindly follow the novels word for word, then go right ahead, just don't expect the world to follow along with you. They aren't canon, even if they are written by the creator, because they were written after what the screen writers intended, and what the screen writers intended is what we got on the screen, it is what we all know, and it isn't creative license.