If I had to give a grade to this book on 100 % I'd give it a 70 %.
Let me explain; 1) I did not like the main character 'cause for me, she was kind of in retreat in this story she gets used and never has an opinion on what to do; first she was taken away by the Darkling though she did struggle and when she fled him she followed Mal around. She doesn't take her life in her own hands that's what perturbates me. 2) I did not like Mal. Perhaps it's because we don't get to know him profoundly 'cause he has a minor role in the book. I think I would like him If I knew him as Alina does. 3) The plot twist is a bit confusing and the Darklings affection is unexplained. Though I see why they fell in love with each other, Alina and the Darkling, the Darkling was a little too quick on his emotions. Well, I don't know if I'm right or wrong but it's my opinion.
Okay so these the bad thoughts let me give you the good ones;
1) The storyline is well done and I can see that Leigh Bardug did a wonderful job in world-building I really felt like being there while reading. 2) Apart from ALINA the character's were intriguing, yes Mal too. My favorite has to be the Darkling 'cause I can just see that he has a tender side to him and that even though he is the villain of the book, I adore him!! He is similar to an iceberg, we saw only the tip of the iceberg but I hope to see him in his entirety in the two sequels. 3)Though the plot twist was confusing, I did not see it coming and on top of that when Alina discovers it I still don't believe it. Plus I always figure the plot twists before they occur and this time I did not so it was rather refreshing to be surprised.

I didn't guess the end AT ALL; it was unpredictable!!!!