The 5th Wave

By Rick Yancey

So aliens have decided to attack humanity. So far they have released four waves of strikes. The first wave took out technology. The second wave was huge tsunamis that attacked coastal populations. The third wave was plague. The fourth wave was assassins whose job is to hunt down the survivors. The fifth wave is to turn the remaining humans against one another. This is done by capturing survivor children and turning them into an army of killers, fooled into believing any survivors they find are either the aliens or are pawns of the aliens and must be destroyed.

This another entry in the teen dystopian novel genre. Our brave young teen heroes are the only ones capable of standing up against the aliens, especially since the author quickly kills off any adults who are left alive.
This is also another entry in the "everyone is a suspect and no one knows who can or cannot be trusted" genre, a common theme in fiction these days.
This is also another entry in the "alien falls in. love with the human" genre.
Nothing that new here, really.

Review from The Guardian.

The Infinite Sea

By Rick Yancey

Book 2 in 5th Wave trilogy.

This book finds the ragged band of human escapees from the alien's training camp living in a deserted hotel in Ohio. Cassie, Ben, Ringer and the other kids are just barely surviving and living in fear of being spotted by the aliens and their human/alien hybrid killers known as the Silencers.
Meanwhile, Evan Walker, due to his alien enhancements, survived the destruction of the training camp, Camp Haven, and has been rescued by a fellow Silencer, Grace, a girl who actually knew Evan before the alien attack. Evan strings Grace along, trying not to reveal that his sympathies now lie humankind and not the alien overlords. He bides his time for as long as he can but finally  escapes, headed to Ohio and the rest of the kids.
Ringer, one of the more capable kids in the group, is sent out on a mission to find a cave system they read about as a possible refuge for the winter, as the Ohio location is too dangerous. She is followed by Teacup, who was supposed to stay behind. They are both captured by the aliens and Teacup is used as a tool to break Ringer, both physically and mentally.
Evan shows up at the hotel, just in time to warn the remaining kids that the latest arrival, a little girl named Megan, is actually a walking time bomb. Unfortunately, Grace shows up and she is focused on killing everyone in the hotel, including Evan. The kids fight for their survival and manage to escape just as Evan detonates the bomb that was attached to Megan and the whole building is destroyed, including anyone left inside.
Back at the alien base, Ringer is getting to know her attendant, Alex, who she calls Razor. She gradually converts Alex to her side and together they plot their escape. Which will be made much easier by the biological implants the aliens have installed in Ringer's body, against her will. Together she and Razor bust out of captivity and steal a helicopter and little Teacup.
But you can't trust anyone and Ringer soon finds herself betrayed and captive once again.

The first book was depressing. This one is even more so. There is a lot of brutality and people getting beat up and hurt and killed. I found it to be way too violent for me to enjoy. I also find combat uninteresting and usually skip those parts, of which there are so many in this story. I doubt very much that I will read the third book in the series. I only read this one because I bought it when I bought  the first book. My mistake.

See also a review by The Guardian.