I'm Not Saying It's Aliens...
But It's Definitely Aliens
 
The weight of the stars
by Kayla Ancrum

After a horrific accident brings loners Ryann and Alexandria together, Ryann learns that Alexandria's mother is an astronaut who volunteered for a one-way trip to the edge of the solar system.
Sky without stars
by Jessica Brody

A futuristic reimagining of Les Misérables tells the story of three teens from very different backgrounds who are thrown together by the looming threat of revolution on a French planet colony. 50,000 first printing. Simultaneous eBook
Mars One
by Jonathan Maberry

"A teenage boy leaves for Mars as a colonist with the Mars One space program and grapples with what he's leaving behind to do so"
We are the ants
by Shaun David Hutchinson

Abducted by aliens periodically throughout his youth, Henry is informed by his erstwhile captors that they will end the world in 144 days unless he stops them by deciding that humanity is worth saving. By the author of The Five Stages of Andrew Brawley. 
What goes up
by Katie Kennedy

Teenagers Rosa and Eddie, trainees in a top-secret space exploration and research program, must thwart the aliens' Earth-destroying mission by stealing their spacecraft and traveling extra-dimensionally to an alternate Earth.
I am number four
by Pittacus Lore

In rural Ohio, friendships and a beautiful girl prove distracting to a fifteen-year-old who has hidden on Earth for ten years waiting to develop the Legacies, or powers, he will need to rejoin the other six surviving Garde members and fight the Mogadorians who destroyed their planet, Lorien.
Losing the girl
by MariNaomi

As Blithedale searches for a missing girl, rumored to be abducted by aliens, a group of high school students experiences a series of romantic relationships and their effects on friendships.
The prom goer's interstellar excursion
by Chris McCoy

Witnessing the girl of his dream's abduction by aliens moments after she agrees to go to the prom with him, Bennett hitches a ride into outer space with a band of extraterrestrial musicians to rescue her.
Rush
by Eve Silver

Pulled from her carefully controlled life through time and space to land in a chaotic game where teen teams are sent on missions to eliminate beautiful and terrifying alien creatures, Miki follows the guidance of a secretive, maddeningly attractive team leader, Jackson, who explains that their choices will determine their survival. 
Dark energy
by Robison E Wells

When a massive UFO crashes in the Midwest, causing profound changes throughout the world, Alice is forced to relocate to a nearby boarding school so that her NASA director father can investigate. 
The expedition
by S. E. Wendel

Hugh and Elena work as apprentices among 50,000 residents of a dying earth on a grueling seven-year journey to their new planetary home, while a young Charneki girl prepares to take the throne and lead her people in the face of the prophesied invaders from the sky.
Alien invasion and other inconveniences
by Brian Yansky

When aliens quickly take over the earth while he is in school, Jesse is shocked to discover that everyone he knows and loves is suddenly gone and that he has been enslaved by an inept alien leader, a situation that is aided by new friendships and Jesse’s fledgling telepathic powers.
Sanctuary
by Caryn Lix

A prison guard-in-training is taken hostage by the superpowered teens of the Sanctuary space station, where he is forced to ally with his captors when the station is attacked by mysterious creatures. A first novel. Simultaneous eBook.