I am a fan of the genre, addicted to Hunger Games, Divergent converted, I read a lot of dystopian novels, very good, and the bad.
With the 5th wave, I was expecting a very good, because I was very attached with the summary, halfway between The Host (very good frame, when we get to overcome the prejudice that the author is Stephenie Meyer), Contagion, Walking Dead and Independence Day and others. In other words, the ingredients, it was heavy!
What I expected with such a summary, it was an apocalyptic world, human responses in survival mode (rule # 1 Cassie is the right "not to trust anyone," but poorly operated), of dilemmas (promises we can not keep), in short, a hard world, where Cassie is forced to grow up very - too fast.
And I wanted a page-turner. There was plenty to make one. And actually the first 150 pages are very catchy, we do not loose them. And the instant Cassie describes the moment she arrives in the refuge "Ash" with his father and brother, and where one sees Zombie, it's over. The events are linked together without real connection, the characters have predictable reactions, everything is a little mess ... even some very good ideas, such as the very complex character of Evan who deserved to be better developed.
In summary, I think the author started his novel too soon. The 4 waves, we would have liked to see them more, to focus on the characters, to better understand what Cassie loses. And the second half of the novel deserved to be better thought.
This remains a good read, a book let loose with difficulty, and which is expected later. But not the slap that I hoped reading the other comments.