Katsa is a graceling - blessed with an ability (in her case, ability to kill easily) that marks her as different. Her uncle, the king, uses her as his personal enforcer, sending her out to hurt those who displease him. On one such trip, Katsa encounters a young man, a prince from a neighboring country, and after that, their fates will be entwined as she must learn to use her abilities compassionately and not as her Uncle's thug. But he has a secret grace and she will be drawn into politics of the world on a grand scale. 
 This is a stand alone though there are two other books in this same world (one a prequel of sorts and the other a sequel but both with different characters). I did feel the book floats around quite a bit and lacks a good solid structure. As well, it can get tiring hearing Katsa echo the same thoughts over and over. Yes, we get the idea you don't want to marry. No, we don't need all the guys falling all over you even though you're supposedly deadly. And yes, we have a hero who is once again just a bit too good to be true.