I recommend Dark Triumph. 
 A triumph indeed. :) R.L. LaFevers? I am now a fan. 
 This was an emotional read for me. Dark past and even darker memories of Sybella are too raw to comprehend in just one sitting. I remember being emotionally spent after reading Dark Triumph. You just don't get that kind of heavy story everyday in YA! And Sybella and Beast's story is so, so good, it left me in a melancholy mood for awhile. A contradictory effect, is it not? I know. I really liked Dark Triumph, but the feels stirred in me was not good for my health. Haha! 
 (I'm going mad like Sybella. Please, don't mind me.) 
 In Grave Mercy, I thought Ismae had it worst. But Sybella takes the cake. Family is important, right? Very important especially in protecting their own. Sybella's? Man, what crackpots they are. Unbelievable, even. But Sybella used the hurt to become a better person, a worthy assassin. It took her a long time to see past the ugliness of what she calls her life. And with Beast? wow, it was truly beautiful to love despite the torment of her past. 
 R.L. LaFevers's writing was intense and moving. I cannot count how many times I want to get depressed with Sybella, or exact vengeance with her. The experience left me tired, but I think it's a good one. A hopeful ending for someone as scarred as Sybella. 
 Dark Triumph is a sequel you don't want to miss. If I was the one who wrote this, and you ask me what do I think of it? I would say that the book was very, very personal