Let me start this review by addressing my 2 biggest disappointments.
1) Alfie and his true intentions. As a fan of this genre, I have pinpointed him a suspect from his very first appearance, as well as all his succeeding moments that weren't at all directly incriminating. And yet, admittedly my own fault, I chose to hope that the trope of "a friend of lead character's deceased parent turns out to be bad" was not the case here. So yeah, the very subtle (as done masterfully by Ryan's writing) yet not so subtle (in comparison to my experience with other stories) hints about his alignment was truly aggravating to me. Especially the part where he selfishly chose money over other people's lives. I am usually a villain fan, but this is the kind of villain that I absolutely abhor. Then again, that is the purpose of his character for Max's personal story, so all that said, it's still pretty solid.
2) Another of my grievances is the lack of personal interactions between the cadets. Throughout the series, we have seen their friendships go from rocky starts to rock solid loyalties. Add that with the humor, quick wits despite their precarious situations, the cadets all had such depth of characters that mixed together incredibly. Understandably, because they were being chased by the titular "Assassin" /s through a rough snowy mountain, there was barely room for such interactions, but again, this had been a huge part of my enjoyment of the series. I also love the individual character moments to highlight the different leads' strengths and weaknesses. I didn't get much of that here other than with Max.
My nitpicks aside, I would be remiss to discard this story. It may not be my favorite, but it is still a class above so many other stories I have read. Ryan's mastery of making such vivid, tense life-threatening scenes coupled with the cadets' quick smarts is always a delight to witness. Not only do I get to join such a thrilling ride while reading, I also manage to learn a lot of survival techniques. This applies to all the books, but for this final one particularly, when it comes to subzero terrains.
I would truly love a continuation of this story with these characters, even go as far as maybe see them become Watchers themselves. It brings me such delight that they all made it out alive. Again, another kudos to Ryan for writing such compelling characters, while brilliantly crafting such perilous situations that make you wonder if the characters could all come out of it, or some may not. I'm happy that for that part, at least, my initial guess of many fatalities in the cadets' ranks were proven false, and we get them all surviving together in the end.