An enjoyable return to Baxter's Xeelee universe, though not the best entry point for new readers. Endurance contains a handful of short stories and novellas from various points throughout the extensive Xeelee future history, so there's a detailed backstory behind each, explored in one or more previous novels. If there's a loose thread connecting the stories it's Michael Poole, the legendary engineer, builder of wormholes, and primary character of one of the earliest Xeelee novels, Timelike Infinity.
The first stories are set relatively early in the Xeelee timeline, between Poole's era and the Qax Occupation. Return to Titan features the hubristic Poole and colleagues on a disastrous mission to the titular Saturnian moon. Starfall is from an epoch we've rarely seen, when humanity has begun the optimistic First Expansion and has yet to encounter any of the Galaxy's hostile species, but revolt is brewing in Earth's own interstellar colonies. Remembrance follows the brief Squeem Occupation. Endurance is set during the Qax Occupation, and like Starfall, connects directly to the events of Timelike Infinity: here we learn some of what occurred on the other side of the time bridge established by the GUTship Cauchy. The Seer and the Silverman features the Silver Ghosts, one of the first species conquered during humanity's genocidal Third Expansion, as well as a curious callback to a revolutionary FTL drive from The Quagma Datum.
We then make a million year leap into the future for Gravity Dreams, which is a loose sequel to Raft, before making an even greater jump for the five stories of Old Earth, which proceed directly from The Siege of Earth (collected in Resplendant). Half a million years after the Transcendence, the Xeelee Scourge reached Earth, and humanity packed the home world off into the deep future, preserved in a well of stratified time. These are probably the least accessible to new readers. It's an archetypal Baxter scenario - civilisation has long fallen, and the survivors attempt to survive amongst the ruins while dealing with a bizarre environment and piecing together the mysteries of their forgotten past - but the story feels unfinished and rather inconsequential.
Overall, a must read for anyone who's been invested in the Xeelee history since the early days of Flux and Raft. There are clearly still mysteries to be revealed, and the stories here create more loose ends than they resolve - and I'm starting to lose count of the various copies of Michael Poole left scattered throughout spacetime. Some of those threads will undoubtedly be picked up in the forthcoming Vengeance - in which the Xeelee evidently attempt to erase the original Poole from the timeline, which would have a dramatic effect on human history. Despite reading the endgame of the Xeelee Sequence twenty years ago in Ring - the Photino Birds win, the Xeelee flee, and a handful of human survivors make it to other universes - it feels like Baxter's still planning some big events, and there's far more going on than has yet been revealed.
There are some curious hints from the coda to Endurance, from Transcendence, and from the older core novels, after which you can't help but wonder if The Friends of Wigner really are nothing but a desperate cult, or if they might really be onto something after all....