One thing is certain, this book is a lot more realistic in the dystopian sense than a lot of other current ones. However, somehow recently this re-imagining of aliens as 'entities' The Atlantis Gene or The Host seems to be around a lot, I am sure if I tried I would find more examples. 
 Regarding the narrative, in my opinion Cassie pulls the whole book through. Personally, the other points of view are unnecessary. It it was entirely from Cassie's perspective we could be left wondering if things are really as bad, if it isn't only in her head, who the 'good' and 'bad' guys really are. With the narrative as they are I guessed the Silencer and the 5th Wave (I'd had the 'Toy soldiers' song stuck in my head since I noticed it about the camp Haven) pretty much right away. Also, her narrative is hilarious, so I hope there's more :) 
 However at the end of it there are a lot of questions hanging and inconsistencies that I hope get cleared out in the following two sequels.