Defending Elysium by Brandon Sanderson

In a near-future where instantaneous interstellar communication provided by enigmatic aliens underpins human society, a uniquely immune security operative uncovers a conspiracy that threatens the fragile peace and a hidden sanctuary. Pursued by assassins and mired in corporate and political intrigue, he must decide how much truth to reveal while racing to protect both humanity’s lifeline and the delicate alliance holding the stars together.