Conflicted between 3.5 and 4, but leaving as it is for now. 
 I enjoyed this book way more than I enjoyed Throne of Glass, though it was by no means perfect. There were still a few things I found fault with, which I will mention: 
 1. Celaena finding the secret door in the library. I found this unbelievable to say the least. In the first book, I found it unbelievable that she just happened to find the secret door in her room (as a champion - as a PRISONER - with a high likelihood of attempting to escape, would they not have properly checked her rooms for things like this? (view spoiler)[Especially as it turned out the king KNEW about this secret area ... though it WAS implied that there were other entrances ... but can we be sure? (hide spoiler)] However in the first book I managed to shrug it off, like okay whatever ... but a SECOND door ? In the PUBLIC (kinda) LIBRARY ! Come on now, this is a little unbelievable, however big and old the library is ! 
 2. Baba Yellowlegs' defeat ... Okay, so this is probaly a spoiler. (view spoiler)[When Celeana is fighting against Baba in her own trailer (and why would you be dumb enough to go in there?!...) Baba specifically mentions all the WARRIOR girls that she has previously had in there: the implication being that she has ... ate them, or whatever. But of course, Celaena is able to defeat this extremely old witch completely by herself, right ? Because she is an awesome assassin. Okay ... Though later she is unable to defeat that creature in the catacombs without the help of Dorian and the use of magic ... Like what? (hide spoiler)] 
 3. The ROMANCE. When they got together, the plot seemed to have got slightly derailed because of them fucking. And seriously, who can even fuck that much. I couldn't ... not least because I'd get terribly bored. (view spoiler)[ I was so fucking glad when that little romance ended and the plot finally went well on its way again. Even when Chaol and Celaena were so obviously still pining after each other ... and where the hell did the L word come from ? Oh my god, calm down. It doesn't help too much that I am NOT a fan of Chaol I guess. (hide spoiler)] 
 4. CHAOL. God, what an annoying bossy asshole. Celaena is an ASSASSIN and has been for like ten years or something, what is he even DOING fussing over her like that and treating her like a child ? Seriously, at one point I was almost grinding my teeth he was so annoying ! Also, he's so totally lying when he says how he is 'not territorial' like damn if my boyfriend started acting this jealous and protective of me I would dump his ass ! What is even the point in him ... 
 Okay, so those were the things that annoyed me, but there were also things that I enjoyed, namely some of the other characters, but also the aspect of magic: 
 I personally thought that the magic was better incorporated in this book than the first. In the first book I almost felt like the magic had been put in there as an afterthought, a quick way to make the book seem more interesting (though this is not the case I believe(view spoiler)[ because that anagram was so well thought through, much else must be, right ? Ah! Time's Rift! Actually meaning I am the First? Bangin'. And relating to magic. (hide spoiler)]). However in the second, the magic seemed much more built in to the storyline and to actually have an importance in the story OTHER than to make it more interesting, and now seems integral to the plot. 
 Celaena: Some people (including my cousin) have been annoyed at Celaena's reluctance to actually assassinate, and I think it is more understandable for seeing why this is if you have read the prequels, and part of it is explained(view spoiler)[ with her freeing of the slaves in The Assassin and the Pirate Lord and the way Arobynn tricked her and treated her badly, to being sent to the slave mines by the very king she is assassinating for. Also in these books you also see about the death of her parents (by the king she is meant to be assassinating for, again!)... and later when you find out who she actually is (hide spoiler)]. I actually LIKED this, especially as it was shown that if someone did do wrong, she would have no trouble actually assassinating. I might have felt differently if this was not the case. (view spoiler)[Celaena being fae - and the fae princess/queen of Terrasen - was pretty predictable. But hey, maybe it'll be more interesting now that she is going away to a place where I think (definitely hoping) that there are more fae. (hide spoiler)] I also thought that her breakdown was important to the plot and to her character as a whole, and was not overdone ... especially not as overdone as her horny romance! 
 Dorian was annoying at the start, though not AS annoying as Chaol. The main reason for Dorian's annoyingness was his pining for and bitterness over Celaena, like ... we get it dude ! The second thing was his indecisiveness and inaction. He was LIMP (yes that's a pun) like a sad, soggy, wet lettuce leaf. However, during this book he really turned it around and I found myself liking his character a lot more after he stands up to his father to at least a small extent. He also is there from Celaena as a friend without expecting anything more from her, which I also found very good. (view spoiler)[I thought that his magic was perhaps a bit too convenient and in this book he did not really do a lot with it (and I kinda wish that - though it is the one important thing his magic DOES do - he had not stopped Celaena from stabbing Chaol, the asshat!) but I hope that this is not the case in the later books and it turns out that it is actually important, and I think that this will be the case ... (hide spoiler)] 
 Nehemia was beautiful. I loved her from when I first met her in Throne of Glass and I was so worried she would be a horrific bitch ! The whole way through I loved her, and I am so glad that there was the confrontation between her and Celaena about Celaena being selfish and passive / assassinating people for the King they all hate ! Before that, her turning a blind eye to Celaena's actions and still being Celaena's friend didn't ring quite true for me, though I could still see her discomfort with this aspect. (view spoiler)[I still love her even though she lied to Celaena about so much ... and I was mad about her death, seriously ! I was happy that there were more female characters that didn't turn into horrible characters, but instead she was killed ! :-( Super sad ! (hide spoiler)] 
 Archer was a very interesting character to me, and I really liked him actually. (view spoiler)[I did not expect him to be one of the 'villains' of the storyline, and I was actually quite shocked when I read his confession of Nehemia's murder/assassination ! I thought that he was one of those characters that Celaena could trust - especially as they had known each other from when she was younger-, and though I did become suspicious of him after the warehouse scene (or maybe a little bit before), not to the extent that I should have been, as was revealed ! (hide spoiler)] 
 Overall, I really enjoyed this book, though there were a FEW things that irritated me slightly. One of the best parts of the novel for me personally was the characters, and I will look forward to their continuation in Heir of Fire!