Graceling by Kristin Cashore is the first of a trilogy. Katsa is a graceling — her extraordinary powers marked by the mismatched colors of her eyes. Her grace is survival — but her uncle, the king, has been using her as his personal assassin.
Katsa, though, we learn has had enough of being as assassin at the whims of an irresponsible king. She has started a secret society to protect against this type of abuse. It is through one of these missions that she meets Po — another Graceling with the ability to know who is where and what they are thinking.
They end up together working. Each mission puts them in more an more danger. If they are to survive, they have to learn how to trust each other.
Early on the book is slow going. There's plenty of adventure but Katsa waffles between blindly accepting her role and hating her grace. It's really not until she finds Po and he pushes her in the direction of the BIG PLOT that things are able to get going.
There are also frustrating inconsistencies. Katsa, for the most part, acts like an adult and she certainly seems to have enough of a back story to be in her mid to late twenties. But then it's hinted here and there that she's a teenager and woefully naive about certain aspects of being a woman.
Then there is Katsa's grace. For the first 2/3 of the book she says her grace is killing. But later when she is forced to survive, and keep those with her alive too, her grace expands beyond the initial abilities. It's then that she says her grace isn't killing, but survival. Coming so late in the book, it was a jarring reset of the accepted rules. It also lessened the drama of crossing the mountains because of course she'll succeed and of course her charge will too.