Young Adult Literature, Science Fiction, War Drama
Like a lot of young adult (YA) literature, The 5th Wave is heavy on young characters and light on adult characters.
Maybe that's because all the adult characters are either a) dead or b) evil. No one wants a book from the point of view of Vosch.
And there's another thing that aligns this book with the rest of the YA genre: it's the first out of three—oh how we love thee, trilogies—and deals with death and destruction in the same breath as first love. Compare it to any of the major YA franchises of the last ten years or so (The Hunger Games or Divergent), and you'll see similarities.
It's also pretty clearly marked as science fiction, what with all the aliens. Like the pod people from Invasion of the Body Snatchers and the cylons from Battlestar Galactica, Yancey's aliens appear to be human, which causes a lot of confusion. Though we "meet" several aliens, including Evan and Vosch, we don't understand much about their motivations. The aliens' inscrutability (that's a fancy word for the way they keep us guessing) seems like a throwback to War of the Worlds, an influential novel by H.G. Wells.
Finally, The 5th Wave is a war drama. Ben, who narrates nearly half the story, is a soldier, and we spend a lot of time with him and his crew in the barracks and in battle. Unbeknownst to Ben, his superior officers are aliens who have disguised themselves as humans. Also, Evan defects from the aliens to help his human girlfriend, Cassie.
And how can you ask for more war, or more drama, than that?