The Lost Planet

The Progenitors-ancient, powerful rulers of an empire spanning a thousand suns-vanished before mankind discovered the Americas, leaving the Elders to rule as Regents of the empire. Three thousand years later, the Regency set their sights on the Terran Republic. When the vast Regency fleet attacks, the fate of humanity falls on a pair of young shoulders. Elise, a scholar's daughter who has never been on her own.
Glen, the slave of an alien master, who doesn't know how to be human.  Against the vast empire, Glen and Elise have nothing to oppose the aliens but their wits, a spaceship, and a handful of allies-an ethereally beautiful alien artist, her equally handsome brother, and a quadruped mob boss protecting her teenage daughter. Together, they must steal a sacred text out from under the Regency's very noses, rescue Elise's father, and hope he can solve the mystery of the Progenitors' whereabouts.
If he can, they must pray humanity's salvation can be found on. The Lost Planet.