What an excellent book! This is the fastest-paced DWJ book I've ever read, and several of the revelations at the end truly surprised me without seeming unreasoned. There were many powerful moments, both action- and emotion-based, and some great characters. There's a cast of zillions, but you get the hang of everyone pretty well. And of course, the book is full of Diana Wynne Jones' perfect word choices ("a tuft of flame"), neat critters and spells (Friendly Cows!), and great descriptions of feelings. I love that she's not afraid to make good characters feel jealous of other good characters who are stronger, smarter, etc. They feel jealous, and they feel bad about feeling jealous of someone so nice or helpful - just the way a real person would. I like that good characters can genuinely like, respect, and appreciate each other and still fight and feel envious or annoyed. The jumping not-quite-omniscient point of view, while sometimes frustrating to me, shows this pretty well.
The grittiness, too, is staggeringly well-done - I really get the exhaustion of the characters during the long marches. And the plot itself is sheer brilliance.
*SPOILERS*
Like pretty much all DWJ books, this one has a sudden series of revelations at the end. Because the book is longer than many, this scene of discoveries is both longer and more intricate. Half the characters turn out to be other people, two-thirds of them provide answers to questions or solutions to problems, and everything is tied up in an incredibly complicated package. I'm actually really impressed by some stuff here - the Deucalion revelation and Geoffrey and Sukey's parentage, in particular, seem well set up but I never would have guessed. (I also never saw Barnabas' betrayal coming.) Brilliant.
I also think Kit's fake death is one of the most convincing I've ever read. I'm enough of a longtime fantasy reader to know that if you don't see a body, possibly with the head ten feet away, he ain't dead. This one is very well done, though. What's more, Kit's family's grief is so strong that I found my cynicism slipping - it's hard to keep saying, "Well, I know he's alive and will reappear later," when his family is sure (with good reason) that he's dead and they're so sad!
That's most of what I have to say, but I will conclude with a brief list of people who got better in the end than I thought they deserved.
1. Querida. The crazy crusty magical old bat bespells Mara into leaving her husband, tries to kidnap Callette, and mercilessly dooms Derk to fail in every way. It's only through luck and the intervention of other beings that half of Derk and Mara's family didn't die for real. I think Querida's new job, fixing their world, could be made to sound like just a little bit more of a punishment - after all, it's going to be a lot of work and trouble - but in a sense, they almost make it seem like a reward, what with her extended life and apparent new strength. And personally, if I'd been Mara or Derk (or any of their kids), I'd have thrown a pig at Querida's head. I guess they're just too happy to be back together.
2. Geoffrey. I don't actually have problems with Big G; I just don't see much reason to like him other than his making Shona happy. He's bossy and seems sort of too shiny and great. The only indication of his being less than "perfect" is that his feet blister after weeks of marching. What? :P Seriously, he kind of takes the Party over from Blade right away, steals Shona's attention with his dazzling-yet-totally-undeveloped character, and even bums Derk out by insisting on taking care of Shona himself. I didn't want anything actually bad to happen to him, and I'm fine with him staying with Shona; I just would have liked to see him fitting more neatly into her really cool family - maybe being forced to bow to the smarts/judgement/abilities of Blade or Derk.
3. Sukey. Again, not hating her, but I don't think she's one of DWJ's stronger examples of the seemed-to-be-annoying-but-really-isn't character, a type she ordinarily does really well.
4. Mr. Chesney. I would have thought his punishment was fair, except that Barnabas sets the bar pretty high by having his soul devoured by a demon in front of everybody. Barnabas is a total traitorous douche, yes, but Mr. Chesney could at least have been eaten by something . . .
I do really love the endings for Kit and Blade, the demons (Awww?), and Umru. This book is epic, and I was super-impressed. Go DWJ.