I was thinking last night that one of the things that bugs me is early on, when Merriman says to Will something along the lines of "None of us has feelings that are of any importance whatsoever compared to the importance of this quest." He's talking specifically about the Drew kids being narked off about Will's presence, but taken out of context it just seems like a fairly profound mistake.
The whole point of Greenwitch is that feelings do matter. Genuine compassion matters and is important, something both the Light and the Dark would do well to remember, because both of them are pretty happy to dispense with it as it suits them. The Dark tries cajoling and then threatening the Greenwitch, while the Light uses logic and reason to try to appeal to a sense of justice that doesn't work the way they think it ought to. But none of these things matter in the end; only a random, heartfelt impulse on Jane's part.
Not insignificantly, I think, it is a female child who succeeds in this quest. All the other players from Light and Dark are male, and the men just aren't getting it. The Greenwitch is nominally female, and will belong to Tethys, who is definitely female. It's no surprise, in some ways, that male attempts to control and manipulate the situation fail - which isn't to say that Jane succeeds because she's deliberately trying to use her feminine wiles; more that her natural instincts work because this is not a Boys' Own Story, it is a story about the eternal feminine.
The other thing I noticed is that on many occasions, the Light just seems kind of stupid. Captain Toms, for example, takes so long to realise what the Dark painter is doing when he's painting the spells of Mana and Reck and Lir in the dark, or even realise that it is important to suss out the situation. Will thinks the Greenwitch is talking about him when she refers to "the child". Partly, of course, this is because it's a kids' book and the main action is reserved for the kids, so the adults have to necessarily be dense and not quite with it. Will, who behaves like an adult (from the perspective of the Drew kids) is much more grown-up in this book than he was in TDIR, but does straddle the boundary somewhat.
But that other kind of dimness I think is related to a kind of intelligence the Light just doesn't have. They have book-learning and arcane magical knowledge. They seem to be a bit lacking, however, in emotional intelligence and just plain common sense. Merriman as a professor is no accident, I suspect; the Old Ones all project that same kind of avuncular absent-minded professor-ness. Well-meaning and helpful to an extent, but emotionally absent.
And finally, something that bugged me in TDIR and bugged me again in this one: choice. The Drew kids choose to participate - Jane after Merriman promises that no lasting harm will come to any of them, especially Barney. But they choose blindly, from loyalty and faith rather than through actually knowing what they're choosing. Captain Toms taking advantage of that and making the Drew kids forget that they've seen Will and Merriman jump off a cliff instead of actually, hello, explaining that it's okay, they're special agents of the Light and they can do that kind of thing doesn't show a lot of confidence or faith in the kids in return. It seems particularly rich, given the Dark painter's attempt to make the Simon and Barney forget using his cheap trick potion in the orange soda.
Which brings me to yet a final point: the Light as manipulators. We already saw this in TDIR with Hawkin, but Merriman's at it again, using the Drew kids to do what he cannot. I'm sure there's some sort of justification in there about humanity needing to choose to help the Light and pay any price, but using kids seems a bit under-handed. It makes me wonder just how he set himself up as a friend of the family in the first place, how far back the manipulation went. How much does he know in advance? If he really is Merlin, he might possibly know the future (or a possible future) and have engineered the whole thing. And I'm not sure how I feel about that.
It's all starting to remind me of the bit in The Last Battle (I think) where some of the dwarves are muttering about the dwarves being for the dwarves, not for Aslan or Tash. But the key difference, I think, is that the Light don't offer the kids an educated choice. I would have a lot more respect for Merriman if he explained the situation to the kids and they knew what they were doing, much the way Hastings (the Dark pseudo-vicar in OSUS) offered the choice to Barney, who rejected the Dark.
There will be more on this subject in the next two books; John Rowlands, especially, is a poignant example. But I'll get there when I get there.