i'm positively surprised with this book. i heard about the instalove and the hurried ending, but I'm pretty happy with what i read. 
 The love story is supposed to be based in a love triangle, and although that is partially so, it is quite obvious from the beginning the nature of both men (view spoiler)[they are the same person, and for me it was obvious I don't know if that was supposed to be a secret since the MC discovered that at the very end (hide spoiler)]. that's, in my opinion, the biggest weakness of this story. i didn't know how but i knew where everything was heading, although there are parts where you don't know what is going to happen next, but i wasn't intrigued very much, i was mostly indifferent. 
 i liked the main characters very much. especially nyx and ignifex, and i loved when they were together, their dynamic was the best part to read and i wanted their parts not to end. 
 and i did like the twist and the ending, although i agree with everybody that claims that it is too rushed. i would even say that is almost a deus ex machina, if it weren't because the thing solving everything at the end appeared before in the story. it bugged me, though, that we didn't get much explanations or more information about nyx and ignifex's ending, but a couple of pages. 
 nonetheless i enjoy the book very much (more the second haft than the first half), i liked that it had greek mythology mixed with fairy tales details (beauty and the beast, bluebeard, rumpelstinskin,...) and the darkness in the story felt different, kind-of "paranormal romance"-ish, but darker... wow, my explanations are sooo helpful #sarcasm xDD 
 in the end, i think that cruel beauty is not a book for everybody, but it is worth the time you spend reading it, definitely :)