Graceling is a first novel by Kristin Cashore. It's really good, and I enjoyed it thoroughly. You should borrow or buy it and read it, and loan it (or buy other copies and give it) to people you know.
The setup of the story is replete with the apparatus of stock fantasy: kings and princes and somewhat mystical powers -- i.e. the tropes and elements that in the hands of someone with less imagination and nerve would be dreadful, but works well when wielded with the right balance and wit. (It works very well here indeed.)
The main character, Katsa, is a young woman (just about 18), neice of King Randa of Middluns, who has a Grace. In this world, Graces are semi-sort-of-magical powers, that manifest themselves in two ways: (1) a very specific skill/talent/power; and (2) eyes of different colors (Katsa has one blue eye and one green eye). Some Graces are benign and in high demand (cooking skills or healing skills); some are less benign but also in demand (fighting skills); others are simply not very useful and are thus not prized -- but these Gracelings are usually mistrusted and mistreated if they have been found wanting by the Kings and Princes of the land).
Katsa's Grace revealed itself when she was eight years old and she reacted instinctively to a leering courtier who tried to grope her -- reacted with lethal violence. From then on, she was trained to be the King's special killer.
Much of the rest of the book concerns Katsa's growing desire to no longer be the King's pet killer, and to change the circumstances under which Kings can do such things. Much of the books' plot is set in motion by the arrival at court of Prince Po from the island kingdom of Lienid, who is also Graced with amazing fighting skills. Katsa dislikes him on sight, which leads in the direction you'd probably expect -- but usually along a non-obvious path.
One of the things I like most about the book is that while the elements going into the story are fairly standard, they're put together in ways that are often quite unexpected. And during the slow reveal of the Main Villain (and I like that there are multiple unrelated villains), the main characters aren't stupid. About three pages after I figured out what the Main Villain is doing and how he's doing it, and just before I started thinking, "Augh! The main characters are dumb! How can they not see it?", they figured it out. Hallelujah! Non-stupid characters, not artificially jerked around to not see something that has become obvious to the reader! And then even though they've figured it out, it doesn't help much. Hooray for turning the screw another turn!
(Okay, I'm going to try to avoid saying anything more about the plot. Really.)
There seem to be (broadly) two approaches to background detail. In one, the author fills in lots of details about everything, and that can help ground the reader to feel like the world in the book is complete and fine-grained, but can potentially overwhelm the reader with irrelevancies. In the other approach, things are sketched in quick strokes and details are given only as necessary and/or pertinent to the story, which can streamline a plot-heavy story but can also end up leaving the reader feeling like they're missing the grit of a real world. (My problem -- and I know that this is my problem -- is that my reading brain is too lazy, or in a hurry, to make up details to put in the background, so without a certain level of details, I end up picturing things being very smooth and under-featured -- almost cartoony.) An example of this split (or spectrum) in approaches is how walk-on characters are handled: in some stories we learn names for many or all walk-on characters (even horses and other animals), while in other stories, no one gets named unless they're important to the plot. Cashore's work falls into the second category. (David Foster Wallace would probably be an archetype of the first.) Purely as a matter of taste, I generally like to have more details rather than fewer, but in a 471-page book (aimed at young-adult readers both artistically and as a matter of marketing), it does make sense to me to trim that back. (And of course, just because I would like more details puts no onus on Ms. Cashore to do anything to change her artistic choices.)
In summary: I really enjoyed this book and am looking forward to re-reading it (probably fairly soon -- but perhaps I should wait until either just before -- or maybe just after? -- the prequel, Fire, comes out in October). Is it perfect? Nope. (Nothing is.) But it's a cracking good first novel and I highly recommend it.
 Every time I read "Katsa and Po" my silly brain does have a tendency to recite bits from The Mikado. Fortunately, this didn't affect my actual reading of the book.