The promise of "a convent full of assassin nuns" prompted me to pick this historical fantasy up. If someone had told me it's also a YA romance, I might have skipped it -- but I'm glad I didn't. For those who might also hesitate based on that description, take heart: 
 (1) There is no love triangle, just a straight-forward (and slow enough to be almost old-fashioned) relationship progression. 
 (2) There is plenty of other action and intrigue going on and the entire plot does not necessarily depend on the romantic storyline. 
 Slightly spoilery mini-complaint: I was convinced that (view spoiler)[the MC's love interest was going to die, and in fact I'm torn about the fact that he didn't -- hooray the heroic man is alive - but - boo did the method of saving him absolutely have to be for the MC to have sex with him? (hide spoiler)] Because that's maybe a little problematic for me, but I'm often willing to ignore slightly problematic things in the interest of relaxing and just getting lost in a story if it's good, which I think this one was. 
 This book also prompted me to learn just a tiny bit more about French/Breton history, though I don't think one needs to be familiar with said history in order to get into the story.