Fifth Wave by Rick Yancey. From Goodreads: After the 1st wave, only darkness remains. After the 2nd, only the lucky escape. And after the 3rd, only the unlucky survive. After the 4th wave, only one rule applies: trust no one. Now, it’s the dawn of the 5th wave, and on a lonely stretch of highway, Cassie runs from Them.
Twice Lost by Sarah Porter. From Goodreads: Mermaids have been sinking ships and drowning humans for centuries, and now the government is determined to put an end to the mermaid problem—by slaughtering all of them. Luce, a mermaid with exceptionally threatening abilities, becomes their number-one target, hunted as she flees down the coast toward San Francisco.
Darkness Strange and Lovely by Susan Dennard. From Goodreads: Following an all-out battle with the walking Dead, the Spirit Hunters have fled Philadelphia, leaving Eleanor alone to cope with the devastating aftermath. But there’s more trouble ahead—the evil necromancer Marcus has returned, and his diabolical advances have Eleanor escaping to Paris to seek the help of Joseph, Jie, and the infuriatingly handsome Daniel once again.