The most annoying thing about this book is all the repetition. It was in books 2 and 3 as well, but not as much as here. The first four chapters - and certain later chapters to a lesser extent - seemed to be constant repetitions of events leading up to this book. Why do authors do this? Why don't they trust their reader to remember that at the end of the previous book the guy our heroine loves got killed and turned into an evil undead vampire? Does she think that between books 3 and 4 we'll have forgotten Dimitri and Rose made love? That Lissa is the last Dragomir? Precisely what dhampirs, Moroi and Strigoi are? Not only are points from the previous books constantly being summed up, but all the endless repetition about Dimitri was enough to have me pulling my hair out too. 
 Must kill him, the new Dimtiri looks like him but it's not him, must find him, must resist him, want his bites and kisses, but cannot let him have his way, must kill him no matter the cost... on and on it goes. I get the point! You don't need to repeat it several hundred times. 
 Moving on, I'd figured out who Abe was pretty quickly, but Rose, being Rose and thus dense, didn't cotton on at all. I would have preferred some form of resolution with Dimtri's family after she left Viktoria mad at her and just walked out on all the others. Maybe this will be returned to in future books, but I doubt it. 
 I didn't like Lissa's timeline in this book. Rather than following the same timeline as Rose, as it usually does, Read spent her time recounting Lissa's past actions. A couple of days would go by for Rose but only a couple of hours for Lissa. She should have found a better way of showing Lissa's story at the same time as Rose's because I just don't buy that Rose can "fish around in Lissa's head" for whatever had led up to current events. I thought she was pretty much stuck with Lissa's present thoughts and hadn't even realised that she could access her memories of the past. I don't like that development, I prefer the present thoughts. 
 Having said this, I did not suspect the truth about Avery. But that might have just been me being more concentrated on Strigoi Dimitri than Lissa going off the rails. 
 Not entirely happy with this one. It lived up to the standard set by books 1 and 2 but not that set by the ending of book 3. Filled with filler, it lacked excitement, though it certainly contained a lot of emotional pain.