Traitor's Run by Keith Stevenson

Two outcasts. One goal: stop Earth. Earth's Hegemony controls the surrounding alien civilisations with ruthless force. Its aim: dominate the galaxy to protect humanity. On Earth, disgraced pilot Rhees Lowrans is thrust into a job she doesn't want. She sees firsthand how the Hegemony will sacrifice anything - including her - to keep Earth safe. In the Lenticular, Udun - one of the empathic Kresz - is on a secret mission when he learns of the Hegemony's expansion into nearby space. But his warnings are ignored and the Hegemony invades his world and mutilates any Kresz who oppose them. Can these two outsiders stand against the might of the Hegemony? And will the human race survive if they succeed?