Brax (The Tellox, #3)

Ariel Bird has always been out of sync with the rest of the world. Turning eighteen with two doctorates has not helped matters. But it never mattered to her as long as she had her sisters. Only now those sisters have disappeared and strange spaceships have been seen in the night skies again.
Everyone thought the Alien threat had come and gone. They were wrong.
Ariel is about to find out what happened to her sisters.
This is the third and last book of the Tellox series. It can be read as a stand alone but is better appreciated in series order.