After reading the list of inspiration sources at the end of the SA rulebook, it was inevitable that I spotted a few of my personal favorites which seemed applicable but had been left out. I know that everyone else will have at least one Sci-Fi source which has relevance to SA but which isn't there too, so in this thread I, and anyone else who wants to join in, can tell us what SA fans ought to read and why.
I'll start the ball rolling with an old favorite of mine- the Culture novels, by Iain M. Banks.
These are a lot more pseudoscientific than SA, being more like a super-advanced version of Star Trek with all the field technology, hyperdrives and other staples that don't have any basis in real science. Though personally, I'd argue that if a modern scientist can look at a technological device and fit it into his own view of how the universe works without it violating any of the natural laws as he understands them then it doesn't qualify for the title Sufficiently Advanced. But back to the Culture.
The Culture is a nebulous, widespread and extremely advanced society that dominates its native galaxy. It has no laws or economy, with society essentially being an communist, anarchic Utopia. It is held together and guided by the Minds, Godlike Superintelligent AIs which have strong parallels to the Transcendentals, except that they are neither as infallible (lacking the Transtemporal aspect) or as universally benign as their SA counterparts (though most only go as far as being indifferent to humans, as it would be pointless to be hostile to something so far beneath them). People live for centuries, and could potentially live forever, though most choose not to- apparently the Human psyche is, in 99% of cases, not cut out to handle living indefinitely. People want for nothing, and are kept from doing wrong by peer pressure, lack of motivation- why steal when you have everything you want anyway?- and the intervention of the Minds in the more extreme cases even with advanced Bio- and Metatech, a society as vast as the Culture will have the occasional Serial Killer type slip through the cracks.
So, given the primacy of a near-omnipotent Utopia in the setting, how can the stories be interesting? Basically, by focusing not on the Culture itself, but on its interactions with other, usually less advanced societies. Because unlike Star Trek, there's no Prime Directive in effect here. Quite the opposite, in fact, the Culture seems to consider that meddling with less advanced societies is not only allowed, but is their duty. The one universal organisation in the Culture is Contact, which has responsibility for all interactions between the Culture and non-Culture. And within Contact is the open, dirty secret of the Culture- Special Circumstances, the black ops group that engages in all the activities that the Culture looks down on other societies for in the name of the greater good.
The Culture novels can be read in any order, with the only connection being that they are set in the same universe.
Consider Phlebas is set earlier than the other novels, in the war between the Culture and the Idiran Empire which resulted in the dominant position the Culture holds in the galaxy in later novels. It is unique in that the main character, rather than being involved in Special Circumstances, is an agent of the Idirans who works against Special Circumstances in the conflict. He sees this as the only way to preserve the infinite ways of life in the galaxy. As he puts it when arguing with a Culture agent, he knows the Idirans are a brutal dictatorship, and as such will dominate the galaxy for a few centuries before collapsing, just like all the others, leaving people free to go their own ways again. But if the Culture wins- what the Culture absorbs, it absorbs forever.
Use of Weapons is one of my favorites. The main character is a mercenary who's been recruited by Special Circumstances, and the whole book is to me a guide to how adventures run with the SA rules should go. If you only read one Culture novel, this should be it.
The Player of Games is mainly set outside the Culture. The central character is a master game player who travels to another galaxy to a star-spanning empire where your social class, right up to the ruler, is determined by how well you can play a mind-bogglingly complex board game. It starts as a simple travelogue, but at the end suddenly shows the true face of Special Circumstances.
Excession is a book for the Culture fan rather than the casual reader, though it should still be enjoyable for someone without experience of the setting. The Culture is all about peace and plenty, and everyone plays nice because there's nothing they could really want that they can't get without resorting to dirty tricks. This book asks the question, what if there was suddenly something on offer that the Minds themselves were willing to fight amongst themselves for it?
Look to Windwards is a book about the aftermath of a Special Circumstances operation gone very badly wrong. Even Minds make mistakes, and it was inevitable given the scale of space and time they work with that sooner or later they'd make a big one. Now a whole civilisation lies in ruins following a bloody caste-based civil war, and the Culture is to blame.
There are also short stories set in the Culture universe in The State of the Art. The novel Inversions seems to be an intrigue-based Fantasy novel, but to a Culture fan it's obvious that two of the characters are offworlders from the Culture, even if such is never said in the book itself.
And although not set in the Culture universe, Banks has also written other Sci-Fi novels. Of these, I'd recommend Feersum Endjin and The Algebraist as also being suitable SA inspiration.
Neal Asher's Polity Novels
Set post singularity, the AIs have stayed behind and run the show with the acceptance of most humans. Travel within the Polity is generally by AI-run FTL gateways ("Runcibles") although FTL 'U-Space' ships also exist (and are needed to place new gateways. Communications can run through U-Space, and people can be 'gridlinked' via implant into it. There are separatists, and a frontier beyond 'The Line of Polity'. The novels tend to focus around Agent Cormac, one of the Polity's specialist troubleshooters. There are alien objects, renegade AI's, an aggressive crab like race (the Prador) which the Polity has been in conflict with, scary bio-genetic stuff, all in a high energy fast paced mix.