The Shattered Skies - John Birmingham - Bog

Centuries after they were defeated and exiled to dark space, The Sturm have returned.

The Sturm, an empire of species purists, have returned from the farthest reaches of Dark Space to wage a war against what they call mutants and borgs: any human being with genetic or neural engineering. In a sneak attack on the galaxy-spinning networks, they overwhelmed almost all of humanity's defenses, blasting dark code that transformed anyone connected to the system into a mindless psychotic killer. The Sturm's victory seemed complete, their final triumph inevitable, until one small band of intrepid, unlikely heroes struck back.
Commander Lucinda Hardy and Admiral Frazer McLennan used the Armadalen Navy's final surviving warship to fend off the Sturm, destroying the massed power of an entire Attack Fleet. With brilliant tactics, this ragtag crew sent the Sturm running, managing to save Princess Alessia, the sole surviving heir to the gigantic Montanblanc Corporation and perhaps Earth's only remaining senator.
Now left with the remains of a fallen civilization, they must work together to rebuild what was lost and root out the numberless enemies of Earth. The Sturm invaders remain vastly more powerful - and they may not be the only threat lurking in the darkness of space...