Spanning the entire lifespan of the universe, these stories chronicle the rise and fall of civilizations caught in the crossfire of a cosmic war between the Xeelee and the photino birds. The narrative follows various human and post-human entities as they navigate the physical constraints of a universe governed by exotic matter, wormhole technology, and the slow decay of baryonic life. Through a non-linear framework, the collection maps the evolution of humanity from its earliest origins to its eventual confrontation with the architects of the cosmos. The protagonist roles shift across the timeline, focusing on individuals who must adapt to the shifting laws of physics and the existential threats posed by dark matter entities.

This collection is widely regarded as a cornerstone of hard science fiction, praised for its immense scale and rigorous adherence to speculative physics. Readers often note that the stories provide essential context to the broader Xeelee sequence, filling in the gaps between the major novels. The work is frequently cited for its ability to balance complex technical concepts with a sense of cosmic perspective. The narrative structure effectively conveys the sheer magnitude of the timeline, leaving a distinct impression of the fragility of life against the backdrop of eternity.