Most books are canon.
Not by the reasonable definition of canon. The word canon as it applies to books is pretty much either "the group acknowledged as being the work of writer X" or "the acknowledged religious sacred texts". It's
really stretching the usual definition of the word to apply it to a bunch of modern science fiction books by about 30 different people. It's a bunch of books, yeah, and they have a big following, yeah, but
canon just doesn't feel anything like a bunch of Star Wars books.
Yeah, that's splitting hairs and yeah, I've read like 70 of them.

It just gets on my nerves a little bit when people talk about stuff like this in terms usually reserved for 2000 year old religious texts.