This is one of the best utopia/dystopia novels that I have ever read! This goes so far beyond the arrival of aliens and extraterrestrials that it needs a new sub-class in this genre. We innately fear that which is nearly possible but not visible, setting the stage for a page-turner that will not be put down till the reader makes it to the last page. "They" have bombarded Earth from space with 4 waves of ingenious, but very doable, destruction, and now, Cassie and her family, indeed all the remaining residents of earth, are waiting to see what the 5th wave will be. What more can "They" do to those few who remain?