The Shattered Sky

From the back of the book:

Twenty-five thousand years in the future, the solar system as we know it is gone. In its place are the slowly-failing remnants of a shattered Dyson sphere, a vast home to the last of the human race, where a small band of survivors desperately tries to reverse the tide of decay and chaos, and where many forces conspire against them. Of these, the most implacable and mysterious are the alien Others, who seek the forgotten secrets of the Sphere for themselves at all costs.