Iain M. Banks - Excession (.mobi) ~DJAUZZIEMAN~

The Excession of the title is a perfect black-body sphere that appears mysteriously on the edge of Culture space, appears to be older than the Universe itself and resists the attempts of the Culture and technologically equivalent societies (notably the Zetetic Elench) to probe it. The Excession is what the Culture's social scientists describe as an Outside Context Problem, one which a society cannot foresee and is often fatal. A metaphor to help explain this phrase is that of a successful aboriginal culture suddenly finding ocean-going vessels on its shores for the first time.
A group of stereotypical bureaucrats tries to manage the Culture's response to the Excession but is brushed aside by the Interesting Times Gang, an informal group of Minds some of whom are veterans of the Idiran-Culture War, to try to deal with what is by far the most serious challenge the Culture has faced.
Meanwhile a rapidly-expanding race, which the Culture calls the Affront (because of its systematic sadism towards subject species and its own females and junior males, despite being relatively advanced), tries to exploit the Excession by infiltrating a store of mothballed Culture warships and using them to claim control of the mysterious object.
It turns out that the Affront have been manipulated into their grab for power by another Culture faction which thought it was morally imperative to curb the Affront's cruelty by any means, and intend to use the Affront's theft of Culture warships as an excuse for war.
The GSV Sleeper Service eventually takes control of the situation. Its name is the most meaningful pun in the story: outwardly it is an Eccentric (drop-out from the Culture) which dedicates its enormous resources to presenting tableaux of historical events (mainly battles) populated by passengers in suspended animation; but in fact it is a sleeping member of Special Circumstances, the Culture's covert operations organisation. The name of Sleeper Service is thus double-pronged—it is a Sleeper Service to human beings in Storage, and a Sleeper Service within SC, as it has produced a massive war-fleet during the 40-year period it has spent behaving as an Eccentric. It prepares to deploy this fleet during transit to the Excession.
But Sleeper Service has an unresolved issue. Until a few decades previously, the ship operated under another name as a normal GSV, providing a habitat for a vast number of Culture citizens. Two of its passengers, Dajeil and Genar-Hofoen, had had an intense love-affair and, after a series of sex changes, had each become impregnated by the other until Genar-Hofoen was unfaithful and Dajeil attacked Genar-Hofoen, killing the unborn child. After the break-up, Dajeil froze her pregnancy and withdrew from society for 40 years while the ship changed its name to Sleeper Service and started acting as an Eccentric. It carried only one conscious humanoid passenger, Dajeil, for which it considered itself partly responsible.
As a result, when the Culture asks Sleeper Service to help in dealing with the Excession, the ship demands that in return Genar-Hofoen must be handed over to it. Genar-Hofoen is lured to Sleeper Service on a pretext, and only later told that he is there to work with Dajeil to help her recover from her psychological trauma.
Sleeper Service then unloads the passengers who had been part of its historical tableaux. Having converted a large percentage of its internal structure into engines, it easily outruns the very fast ship which other elements of the Culture had asked to keep watch on it. Once it is beyond the watching ship's sensor range, Sleeper Service changes course and heads towards the Excession. When it arrives it becomes apparent it is carrying a vast fleet of remote-controlled warships numbering in the region of 80,000 units. The Excession, in response to the Sleeper charging at it, triggers a multi-light-year Gridfire wave[clarification needed] which threatens to obliterate it and its entire fleet, along with the accompanying Grey Area. Only its Mindstate,[clarification needed] transmitted right at the Excession, saves it by persuading the Excession to halt its attack. The Minds controlling the ships which the Affront stole from the "mothball" find themselves outnumbered more than 130:1 and refuse to fight. The Affront fleet's commander and the Culture ship which led the conspiracy commit suicide. A prolonged war is thus averted. At the same time the Excession disappears as mysteriously as it arrived.
Meanwhile, the rush of events, combined with a conversation with Genar-Hofoen, results in Dajeil deciding to complete her pregnancy. Genar-Hofoen returns to the Affront, having been rewarded by being physically transformed into a member of the Affront species (whose company he finds more stimulating than that of the Culture's people).
The book's epilogue reveals that the Excession is a sentient entity which is currently acting as a bridge for a procession of even higher beings which travel between universes. It also assesses whether the species and societies it encounters are suitable to be enlightened about some unknown further existence beyond the Universe. As a result of events in the story the Excession concludes that the civilisations it has encountered in our universe are not ready for this enlightenment and hides itself so that it will not cause any further disturbance, hence its disappearance at the end of the book. It also takes the name given to it by the Culture – Excession – as its own.