Winter is an extremely anticipated conclusion to the Lunar Chronicles. I have avidly followed the series since its first book, Cinder, was published and even though Cinder wasn't my favorite book, the books that did follow redeemed the series. Considering this is the last novel, I will do my best to not include spoilers and I will evaluate first Winer, and then the entire series. 
 Upon completing Winter, the first word that comes to mind is 'overambitious'. There is just way too much going on. There are four characters - Winter, Cress, Cinder, and Scarlet - who all have significant others they are fawning over and who all have some type of massive mission or quest they need to complete. That would be enough to fill an entire book on its own, but then you throw in the Levana storyline and her effort to overtake the world and it is just too much. 
 So that is 9, yes 9, main characters that are all fighting for page time. Many of the characters - Winter and to some extent Levana - have just recently been introduced to the series, which means they haven't had time to grow and develop, and given the hectic nature of this novel it didn't happen. 
 Unfortunately, because there is so much going on, certain characters and plots aren't given the attention they deserve. It almost felt like every character was literally fighting with each other to get their allotted 'page time'. If done properly, it might not have come across this way, but things bounced around so much that it felt not one character was given the time or attention they deserved, which meant as a result everyone came across as weak, underdeveloped and just disappointing. 
 Maybe the overambitious nature of Winter wouldn't have been so troubling, if the plot had been well-executed. Readers can forgive a bit of a hectic nature to a book if the plot is good, but Winter isn't very strong in that aspect either. Several elements made the plot-aspect of Winter weak; I'll explore some of them here. 
 The first plot issue I had was there was a huge reliance upon 'fake death'. What is 'fake death'? It is when a character is 'killed' by someone, that individual believes they are dead, and several pages/chapters later that character mysterious survived and they are back for vengeance. 
 Fake deaths certainly aren't anything that is new to fantasy novels - or many novels - but Winter just had this happen way too many times. It seemed as if every character was captured multiple times, someone would be just about to shoot/kill them, and then miraculously they would find some way to escape. 
 This didn't happen once, twice, or even three times. It happened over and over and over again. There just comes a point that, as a reader, you have to say "okay, enough", which leads me to my next issue - repetition. 
 Winter is extremely repetitive and not just when it comes to fake deaths. It just came across that the same things kept happening to the characters over and over and over again. At one point all the characters scatter and separate. Unfortunately, they all seem to be experiencing the same thing - go out on a mission, get captured, almost die, and escape. If there wasn't a capture followed by fake death, it was Levana using her powers to be 'evil' and trying to get the other main characters to kill each other even though they didn't want to do it. 
 The repetition could be caused because of the overambitious nature of the book. There is also the issue that there are huge sections devoted to providing the details and information that was found in Fairest (Lunar Chronicles 3.5). Maybe if Fairest hadn't been published, it would have helped with the repetitive nature. 
 Another issue that arose with Winter was our supposed star of the book - Princess Winter. Every book so far has introduced a new main character and Princess Winter and her lover Jacin were the newbies for this book. The thing is they were hardly in the book. If I had to estimate, I would say maybe 5% of this book focused on Winter and/or Jacin. 
 Winter is used almost as a background character. When she was brought up, it had the feeling that it was 'oh yeah Winter is here'. It was a shame because out of all the characters, Winter seemed the most intriguing and fascinating. 
 The last issue I want to address is the ending. It is difficult without giving away spoilers but the way the novel ended was unsatisfying and the tactics used to defeat the 'big bad' were questionable and a bit infuriating. I really wish I could give specifics, but I don't want to ruin the book for anyone. 
 I will admit I was disappointed in Winter. It was a sluggish, 800+ monster of a book that is honestly the weakest book in the series. It was literally 200 pages into the book before something happened, as readers were told all about how the main characters were fawning all over each other and developing their romance. When action did happen, it quickly ended and was back to the sluggish pace. 
 This book could have worked had it been approached in a different way (less repetition and fake deaths) or the main character count had been lessened, it would have been a wonderful book. 
 Even though Winter is the weakest book - in my opinion - I think, as a whole, the series works. I wouldn't say my Winter ruined the series for me, but it certainly left me with mixed feelings on the entire series as a whole. Marissa Meyer is still extremely talented and I would readily read any book she wrote, but Winter just didn't do it for me. 
 If you are a die-hard fan of the Lunar Chronicles, you will certainly love this entire series. I just wish for such an epic YA series, it would have ended differently and the final book had given me the experience I really wanted.