The Skinny: 
 The only time a sequel is better than the first book. 
 The Fat: 
 Wow. I mean, just, wow. This book ended up being so much better than Throne of Glass. Usually in series there is the plague commonly known as "The Second Book Slump" or in other words, the second book is usually much worse than the first book. But Crown of Midnight (COM) was a thousand times better than TOG. The awkward love triangle was quickly nixed. The characters had more depth. The relationships felt less forced. There was more killing and bloodshed and Celaena acted more like an assassin than the previous book. Before readers were only told of her skills, but in COM they were shown. She is cunning, talented, and a complete badass. 
 However, Maas was still guilty of having POV changes too quickly. At times it seemed unnecessary. For example, during a fight scene in the second part, Choal and Celaena changed POV's within paragraphs of each other but it gave no added insight into either. It didn't add to the novel, but rather took away from it. So Maas lost points for that. Also, at times Celaena's inner-monologue was a bit melodramatic. There were also long spans of time where I was bored, or wanted to roll my eyes at her inner-monologue. 
 COM is told in two parts. The first part wasn't terribly interesting until the very end, but part two had so many plot twists I felt like I was going to get whiplash. It was intense. Unfortunately, the terrible thing about reading a book after it has been out for a while--especially when it is Tumblr popular--is that major plot twists were spoiled for me. I can only imagine how reading this book before the spoilers would've been. I assume it would've been insane. 
 There are quite a few new characters who are introduced (Mort is by far my favorite). And Maas leaves people constantly wondering who to trust. There is espionage and trickery and magic plays a much bigger role in this book. Readers also get a glimpse into Celaena's past. 
 This book was a thousand times better than its predecessor. Although it still has its flaws (some of which are spoilery so I can't say what they are), it was still a fun read. There is revenge (I do not want to piss Celaena off) and plot twists and betrayal and secrets (oh so many secrets). If you were ever on the verge of not reading COM based on TOG, then I suggest you reevaluate your decision. TOG had me on the fence, but COM has me hooked. 
 Prepare yourself for a wild ride. 
 ***TRIGGER WARNINGS: death, murder, prostitution, mentions of R, incarceration, torture, forced servitude