I bought Elizabeth Bear's "Dust" about 3 years ago when I read it for an online book club (which has since vanished without trace so I can't even link to it). I did write about it on my own livejournal so I can link to that first impression. This is another of the backlog of book posts that I'm catching up on (the last one! I'm nearly up to date!) so again I think this'll be less in depth than I would've written had I got to it quicker.
The book at first seems to exist in the space between science fiction and fantasy. The opening scene could almost come out of a pseudo-historical medievaloid fantasy - there's a Lady, there are knights, a housekeeper, a named sword, and our point of view character is an upstairs maid. But look at it more closely and you see the science fiction - nanotech chains, references to extruded material, beam weapons. The literal blue blood for the Family (the Exalt, the aristocracy of this world) could go in either camp at this point. Reading on it becomes more clear that this is science fiction - the story is set on a generation ship, a spaceship travelling at slower than light speed where the crew are awake and expecting their voyage to take several generations to complete. But something has gone wrong, and the ship isn't travelling any more and hasn't been for centuries. A lot (most?) of the crew are Means - they don't have nanotech symbionts and their lifespans are what we would consider normal. The Exalt are effectively immortal, and so the older ones were alive before the disaster. You might naively think that would make it easier to keep society together and work on fixing the ship. But the Family are split into factions and in many cases more concerned with their internal political games than worrying about anything else. This isn't helped by the fact that the ship's AI is also fragmented. With a crisis looming the status quo can't continue, so at least the AI is trying to regroup and gather itselves together. Of course, it isn't that easy - each fragmentary personality wants to be the last one standing and will fight with whatever tools it has to achieve that goal.
The first scene also introduces us to the two primary protagonists, who are certainly intended to be tools of one (or more) of these fragments. There is Rien, through whose eyes we see the scene. She's a teenager, an orphan, a maid, a Mean who turns out to have a rather more Exalted heritage than she imagined (pun fully intended). We also see Sir Perceval, a Knight from Engine captured by the Lady Arianne Conn of Rule who has mutilated her and will kill her. Perceval is also a young woman, but fully Exalt and aware of her heritage, and happens to be Rien's half-sister. Their story is of a pattern that's more from the fantasy side of the dividing line - they escape and go on a quest across the world. Both are Chosen Ones in their own way, and together they must try to save their world. No matter what the cost.
It's another book that feels like it would reward going through with a fine tooth comb and noting all the little details. As with the Promethean Age books names are very important, although in these books knowing someone's name doesn't give you power over them per se - this series is after all on the science fiction side of the line. But names, their meanings and the choices behind the names reveal things about the person or object once you're paying attention (whether that's you-the-reader or a character in the story). Choice is again a theme. In this story there's a lot about the horror of having your ability to choose taken away, or your choices coerced. And about how even when you're suffering the knowledge that you freely chose to pay this price for something you consider worth it can bring a certain strength and endurance.
A good book, I definitely enjoyed it as much the second time around as the first :)