We meet our protagonist, Ismae, on what is probably the worst day of her life. She's just been sold off in marriage to a pig farmer who looks and behaves far too much like his charges. But when he is repulsed by the ugly, red scar on her back--the mark of death in fifteenth century Brittany--Ismae is rescued and spirited away to the island convent of Saint Mortain. Even if the place were an actual convent, Ismae would have been happy. But Saint Mortain's trains girls in the arts of death, sending them out into the world to do their god's bidding.
Ismae spends three years in training before being sent out to take her final tests and finds herself embroiled in a fight to keep Brittany independent of France. It seems a hopeless case, but Ismae has faith. Well, she has faith until she uncovers evidence that her beloved convent has been corrupted. The tests she faces test much more than her ability to take a life. Her faith is tested, mostly by an aggravating man who is fighting harder than anyone for the duchess of Brittany.
Grave Mercy reminds me a lot of Maria V. Snyder's Poison Study series. Both feature strong--and deadly--female protagonists. Both feature women elevated from the lowest positions in their respective societies, to circles where they can make a difference in their countries futures. They're the kind of female protagonists that I like to see in young adult fiction because they're logical and determined and not content to wait for someone (male) to come and rescue them. I'm very curious to see what happens in the sequel, when LaFevers turns her attention to a much more volatile protagonist.