The 5th Wave by Rick Yancy

First Wave: “Lights Out” During the first wave, the Others release an EMP wave that takes out all electronic technology and kills half a million people by shorting out all moving vehicles, including planes in mid-flight. 

Second wave: “Surf's Up” The Others, realizing that roughly 40 percent of Earth's population lives within 60 miles of the coastline, drop enormous rods "twice as tall as the Empire State Building and three times as heavy" onto the Earth's fault lines, causing massive tsunamis that wipe out three billion people. 

Third wave: “Pestilence” The Others launch a scheme to infect as many remaining survivors as possible with a deadly virus. Using the Earth's birds as carriers (via falling excrement), the plague claims 97 per cent of remaining survivors. The virus, which resembles an advanced form of Ebola, causes victims to slowly bleed to death until eventually "you've become a viral bomb. And when you explode, you blast everyone around you with the virus". 

Fourth wave: “Silencers” After the 3rd wave, the remaining human population tries desperately to survive off whatever resources remain by looting, all the while clinging to the hope that "the people in charge", wherever they may be, are working toward a solution. Eventually, this belief seems legitimate when an impressive battalion of soldiers (with functioning vehicles) arrives at the makeshift camp where Cassie, Sam, and her father are staying. The soldiers and commander, however, only appear interested in the children and promptly load them onto waiting buses before ordering all the adults into the camp barracks.  Once the humans are surrounded, Commander Vosch orders a massacre and kills everyone at the camp.  Cassie, however, narrowly escapes and witnesses her father's death by Vosch's hand. At this moment, the 4th wave becomes clear: not all "humans" are actually humans.

Cassie goes on a mission to rescue her little brother.  She finds herself trapped and wounded by a sniper.  But eventually, he walks away.  A couple of days later, she discovers another survivor, delirious, she faints and wakes up in his farmhouse.  Her little brother and her fellow survivor are trained in weapons and then sent on a raid to root out the Others.  Only it turns out that their Sergeant is really an Other and the exercise is a trap to remove the best defenders of humanity left alive.