Gregory Benford 
Tides of Light 
Galactic Centre Book 4

Continuing the story begun in Great Sky River, Benford creates a stunning novel of the last band of humans fleeing extinction in the Galactic Center. This last remnant of humanity is led by Killeen, a man elevated to command in desperate times by his luck and daring. He manages to reach a new planet where he encounters vast wonders. But with one enemy behind them, the humans are dismayed to discover an alien race more awesome than any they have encountered.