A Princess who must fight her sister to the death to become queen? Let's read!

The cover of A River of Royal Blood is interesting enough, but it doesn't grab me as much as the story itself. Eva and Isadore are sisters, princesses of Myre. Both have the gift of magick, but Eva's is one that is rare. Nothing is known about it, as it hasn't appeared in anyone for generations. All Eva knows is that her magick is considered savage, and that she can't use it. She has made peace with the idea that, when she and Isadore fight for the queenship, as is tradition, she will go to her death and Isa will be queen. She just wants to spend her last few months of freedom (and life) with as little interaction with her dysfunctional family as possible.

The portion of the book I read for this First Impression ended with a stranger holding a knife to Eva's neck. Who wants to kill her, and why? I need to read this book to find out what happens. It has sucked me in already.