Some people in Cashore's fantasy world have special "graces" or superhuman powers. Lady Katsa's grace seems to be killing. From early childhood, she has been feared. Now she is in the service of her uncle, the King, discouraging unrest by killing or maiming disloyal subjects. But Katsa isn't happy with this life. She has secretly formed a Council that seeks to right wrongs. Katsa meets (and fights) Po, a foreign prince who has a special grace of his own. Together they embark on a quest to rescue Po's cousin. Lots of action and romance. Katsa is a strong female character trying to figure out how to live with her grace. As the Booklist review notes "...from her first kill to her first experience of lovemaking, Katsa’s womanhood is integral to her character".
Graceling was Cashore's first published book. The prequel Fire came out this year. I really enjoyed Graceling and plan to read Fire this summer when I allow myself the luxury of reading related books (my general plan for trying to stay up with YA lit is to not read other books in a series, continually moving on to new authors, new series). Graceling is recommended for grades 8-12 and a good one to suggest to Tamora Pierce fans. It also reminds me of Megan Whalen Turner's Attolia books with their political intrigues. I would introduce it to students by describing when Katsa's grace is first identified: at age 8, a man tried to grope her and she struck him dead.