Grave Mercy is a young adult novel about assassin nuns who work for the god of death.
How awesome is that?
Ismae has been considered a curse, Death's own daughter, ever since she survived an abortion attempt with nothing more than a scar on her back. When her new husband beats her and threatens to turn her in as a witch, she flees to the convent of St Mortain, where the nuns carry out Death's wishes for him. In her first important assignment, Ismae ends in the high court of Brittany, attempting to uncover treason and protect the new young Duchess from threats. She's been told to keep an eye on the seemingly untrustworthy Gavriel Duval, and kill him should Death's mark appear, but as Ismae falls deeper into court intrigue, she starts to wonder if Duval is actually the only person who can protect the duchess... and if she could kill him either way.
There's a lot to love here, beyond the badass premise. Ismae is an "I could kill you with my pinky" sort of heroine, and she's incredibly smart with it, but she's also quite a vulnerable and naive figure underneath, putting all her trust into the word of the convent, and the combination makes some interesting struggles and character growth. We get some glimpses of the other assassins, but the most prominent other female character is the Duchess, a young teenager who is in over her head, but deals with her situation with a lot of wisdom, intelligence and grace. She's far more vulnerable in a fight that Ismae, but that doesn't mean she's not a force to be reckoned with.
Ismae's relationship with Duval is also fun if you like the "bickering turned to love" sort of thing, but their romance (and the duty-bound-assassin-related problems it faces) does become a major focus of the plot, so if you're not a romance fan, that might be a reason to beware.
Also, for an assassin book, Grave Mercy doesn't have that many assassinations. Death and threats are rife, but the middle third of the book is more concerned with court intrigue and machinations than slitting people's throats in their sleep. I found this part just as fun and addictive as the rest, but if you're going in looking for non-stop action, you might be disappointed.
Grave Mercy is like a YA Game of Thrones -- less graphic, and fewer characters to keep track of, but full of scheming, danger and kickass struggling ladies. If you love court drama, awesome heroines and books with the chance that everyone will end up dead, this is a great one to try.