I was initially kind of surprised to see this in the axis of awful, but then I read your actual post and thought back to my own experiences with the books and it's perhaps not that surprising.

I read The Knife of Never Letting Go more than six years ago, loved it and ran out to buy the other two. But I found The Ask and The Answer's relentless pacing and breathless prose so exhausting I felt like I had to take a break before tackling Monsters of Men.

That break kept getting longer and longer, and now the book is sitting on a shelf in my room, unread. Now that I know where the story ultimately goes, I'm kind of glad I didn't bother.

I'm willing to bet that if I went back and reread the first two books I'd probably be far less taken with them- it's been long enough that my tastes have changed significantly, and at the time I was young enough that "it turns out that both sides are just as bad as each other" still felt interesting and somewhat revelatory. When the same theme comes up in fiction now (the example that comes to mind immediately is Bioshock Infinite) I find it trite and not at all useful or worth saying.

On the subject of making a story about how both sides are committing terrible acts without making your protagonists monsters or completely passive- I think perhaps the best way is the noir approach. In other words, have your protagonist be basically decent, but caught up in the world of powers far beyond them, and thus unable to enact more than a little change. A good example of this would be John le Carre- take The Spy Who Came in from the Cold. Lemas is more or less trying to be an okay person, but his attempts can't compare to the ruthlessness of the powers he's caught between. Of course, there's a reason le Carre tends to have downbeat endings, and noirs tend to be bittersweet or downers.

Is it any less skeevy when a female character is fridged to further another female character's story instead of a male's? Somehow I doubt it.

I'm going to have to disagree with you there. I can see what you're getting at, but I don't think it's useful or even possible for a work of fiction to treat every character as equally valuable, for want of a better word, and everyone's story as equally important. Any attempt to try is likely to result in a shapeless, bloated mess. You have to decide whose story it is, and then you have to render everyone whose story it isn't subordinate to the person whose story it is.

To take the example that you've given, it sounds like the two young women are introduced solely for the purpose of getting killed later on in order to motivate Viola. And, to be honest, that sounds perfectly reasonable to me. If he had introduced them, developed them over several volumes, brought you to care about them and then killed them off in a perfunctory manner like poor Lian Harper then that would be something to complain about, to be sure, but I've always felt the real problem with fridging was not that it kills women but that in doing so it disrespects both the characters, the care and attention that other artists have put into them, and the love that they have inspired in the fans. None of which applies when the victim is a redshirt, and all of which conversely can apply when the character dies in a thematically valid conclusion to their character arc (looking at you, Adrian Tchaikovsky).

Okay, good point about the difference between killing off an established, long-running character to motivate another character as opposed to killing off a walk-on. (I may be misremembering here, but I thought I heard somewhere that the original Woman in a Refrigerator was always intended to die to motivate her boyfriend - the Green Lantern - to do something or other, but was still given a good whack of development so that the reader would feel her loss along with him.)

I'm not entirely convinced, but no counter-arguments immediately spring to mind. If somebody else wants to take up the argument, I may or may not agree with them, but I'll let the point stand for now.

I mean, it can also be skeevy if a) female guest and walk-on characters are frequently stuffed in the fridge to motivate the main characters, or b) the tone of the piece gives the implication that this death is especially tragic or heinous because the victim is female, but these aren't always the case.

That said, introducing a character, and developing them just enough to make the reader mildly invested in them as such, and then killing them off to motivate a main character is often a cheap-shot. In this case, from what I remember, there were plenty of other potential motivations for Viola to take the actions she takes. (Another case in point: The Night of the Doctor.)