[Zeke]

Uh, Nate? Those books aren't canon under any definition I've seen -- aside from one's personal canon, which can include or exclude anything.

But it's a moot point, because the dichotomy you're creating isn't one I'm interested in. To me, continuity is important, but not all-important. The thing to remember is that every continuity error can be explained -- and will be, but only if the material is worth the effort. I doubt anyone felt inclined to make excuses for "Threshold," but "Dark Frontier" was rationalized in any number of ways.

If the question is "Did ENT hold perfectly to continuity?", the answer is no. Neither did TNG, DS9, or VOY. Neither did TOS from one episode to another. But the question that matters to me is "Did ENT hold well enough to continuity?" That is, were its mistakes small enough -- and the show good enough -- to be worth making the necessary excuses for? And my answer to that question is an unqualified yes.