Started out a bit slow for me, but this is Victoria Schwab we're talking about so I had no worries. The story just kept building and building towards the finale and as it went I become more and more hooked. I didn't want to put it down or have it end. 
 I loved the idea that monsters form out of the shadows of violence. Three different types of monsters: Malchai which form when an act of murder is committed; Corsai form from violent actions; and Sunai the most rare form out of the most tragic of losses, bombings, mass shootings, etc. They came about after an event called the Phenomenon, where all the built of violent energy just pretty much coalesced and brought forth the monsters. 
 The juxtaposition of monsters and humans, and what it means to be one or the other, or the perception of what it means to be one or the other, is a big concept throughout the book as both August (the "monster") and Kate (the human) struggle with their place in the world. 
 Kate Harker comes from the North side of Verity where her father is the head boss, so to speak, citizens can get protection, for a price, from the monsters who also happen to be in Harker's employ. 
 August Fynn is on the South side of Verity, and he, with his family and groups of humans, fight the monsters everyday to keep them out of their territory. 
 Peace between the North and the South hinges on a quickly crumbling treaty, and it seems as though war is imminent. 
 I liked that Victoria Schwab decided not to form a romance between Kate and August (this may happen down the line, but in This Savage Song it doesn't happen). I think forming anything beyond the tentative friendship would have detracted too much from the message of the book. Plus, I loved seeing these characters who are supposedly complete opposites (although more similar than they want to admit) come together in a time of need and help each other. It plays out so well. 
 Even with the slow start, the ending makes me completely excited for the second book. If you've read other books by Ms. Schwab (either as Victoria or V.E.) you'll see a lot of similarities in writing style, which means even if things are left a little precarious for our characters, you know everything will turn out right.