Axiom, book 1: The Wrong Stars
Tim Pratt2017

A ragtag crew of humans and posthumans discover alien technology that could change the fate of humanity... or awaken an ancient evil and destroy all life in the galaxy.

The shady crew of the White Raven run freight and salvage at the fringes of our solar system. They discover the wreck of a centuries-old exploration vessel floating light years away from its intended destination and revive its sole occupant, who wakes with news of First Alien Contact. When the crew break it to her that humanity has alien allies already, she reveals that these are very different extra-terrestrials... and the gifts they bestowed on her could kill all humanity, or take it out to the most distant stars.