I didn't mean to say that I don't appreciate originality. I think that's something that's sorely lacking in most of todays works of fiction (novels, movies, TV). I also didn't mean to suggest that "blurring" the lines between genres isn't favorable, because it is. One of my favorite series is Eric Garcia's "Rex" novels (Anonymous, Casual and Hot & Sweaty), and the main character in those books is a dinosaur private investigator masquerading as a human. Hard-boiled detective fiction wrapped in a thick coat of science fiction, and (in my opinion), they're tops. Reeses Peanut Butter Cups tops, to continue an analogy.
This is just a matter of these specific characters in these specific novels. I disagree that the series would've become stale without the supernatural elements. I mean, sure, eventually it would've. All series do, usually (I've found) around the 10th entry. Past that it's a rare animal that can sustain a series of any genre. If Dr. Wilson didn't seem to be writing the series to a conclusion already eventually even Repairman Jack would've become humdrum no matter what kind of predicaments he found himself in. In that regard I give him a lot of respect for wrapping up his world before Jack became another Remo Williams (what are the Destroyer books up to now? 115? 120?)
In the case of these characters and stories, I just feel that the two central themes would have been best served as individuals rather than a duet. There's something to be said for duets, of course, but there's also something to be said for solos.
I'm not trying to change anyone's opinion. Just voicing my own.
(And, although I'm sure I've missed some good stuff along the way, I haven't cared for YA fiction since I was a YA myself.)