The Hydrogen Sonata by Iain M Banks.
There comes a time in every major civilisation's life when you sit back and think: hey, we've done it all. Evolved some form of opposable limb appendages to facilitate tool use, used those tools to construct machines to escape our home planet's gravity well and traverse the galaxy, come into contact with other civilisations, some very different from our own, and managed to find a way to co-exist without annihilating each other, made some thought-provoking art about all of the above, stood around and appreciated it for a while; I mean, what else is left to do? Basically it's either the long slow process of decline and decay, or you go out in a blaze of glory and Sublime.
Now this is not like the chemical process of sublimation where something solid vanishes in a poof of smoke and is no more - wait, no, actually it's pretty much exactly like that. Once a civilisation has democratically decided it wants to Sublime - and the bar is set pretty high for an acceptable majority, none of your 52-48 business here - and a date is agreed upon, that's basically it. Assistance is mysteriously forthcoming from the Sublimed realm and on the appointed date everyone who's decided to go (and individual opt-outs are available for anyone who really wants to eke out their existence on a ghost planet, or, more sensibly, hop on a passing spaceship and start a new life somewhere else) just mumbles some mystical incantations and poof, job done.
Tradition dictates that other civilisations who have links to the Subliming-adjacent one send tokens of their esteem and attempt to make good any unfinished disputes in a mutually respectful way. And so it is that a ship representing the reality-bound remnants of the already-Sublimed Zihdren civilisation makes its way to Gzilt space with a message. Once it has been intercepted by a Gzilt ship, though, the whole mutual respect thing goes out of the window and it is forced to reveal the contents of the message it is carrying earlier than planned, and, upon the contents being revealed, is promptly blasted into its component molecules for its trouble. I mean, don't shoot the messenger, right?
Vyr Cossont is just minding her own business trying to master a fiendishly difficult composition (the Hydrogen Sonata of the title) for a fiendishly complex eleven-stringed instrument that she's had a couple of extra arms grafted onto her torso especially to help with. That's Lieutenant Commander Vyr Cossont to you, actually, although everyone on Gzilt acquires a military rank by default and she has no military experience whatsoever. This doesn't stop her being conscripted for a top-secret mission, though; apparently something of crucial importance that could have a major bearing on the whole Subliming thing. But why her, and not, say, someone who knows what they're doing? Well, it turns out that while doing some interplanetary travelling a few years earlier (a sort of space-based gap year) she happened to spend some time with one Ngaroe QiRia, a Culture citizen who may be the oldest human alive, and by virtue of that may have access to some secrets which may explain the Zihdren-Remnanter "incident" and shed some light on the contents of the message being (unsuccessfully) delivered.
Meanwhile representatives of some Scavenger species are circling the various Gzilt home-worlds; these guys move into planets recently vacated by the Sublimed, hoover up all the loot (you really can't take it with you, you know) and sometimes move in, if the atmosphere and solid/liquid ratios suit their crazy alien physiology. Usually the outgoing civilisation confers a sort of Preferred Looter status on one set of ships, so the stakes and emotions are high. In this case the front-runners are the Ronte, sort of big insect-y dudes, and the Liseiden, who are big sentient eels slurping around in giant fishtanks. A delegation of Culture ships is also in attendance, either to provide a calming influence and a neutral party for conflict resolution, or to be interfering holier-than-thou do-gooders and spoil everyone's fun, depending on your point of view, and whether or not you are a giant sentient eel.
Cossont leaves her Gzilt home-world in search of QiRia but is promptly nearly rubbed out on the orders of some high-ranking Gzilt politicians who would rather things just be allowed to take their course without anyone rocking the boat, thanks very much. Rescued by a Culture ship, she enlists its help finding QiRia. Things are more complex than they appear, though, as while the physical QiRia is located, it turns out he's had lots of his memories removed and stored on various mind-state backups in various locations. The relevant memories, it turns out, hilariously, are actually back on Gzilt, in an old pair of QiRia's eyes. So, all back to my place, collect the eyes, see what's on them, have a pint and wait for all this reality to blow over, right?
Obviously it's not quite that simple: for one thing there are hordes of Gzilt and Culture ships having a Mexican stand-off in orbit around the planet, and secondly the eyes turn out to be in the possession of a guy/creature called Ximenyr who is the sort of master of ceremonies for a marathon end-of the-real-world party on an endlessly circling airship. So getting in won't be easy, and getting out next to impossible. Fortunately Cossont has the Culture on her side and those guys do six next-to-impossible things before breakfast. The memories are retrieved, decisions are made about the value of sharing the data more widely at this late stage (literally hours before the Subliming), full-scale spaceship wars are avoided, honour is seen to be satisfied all round and everyone poofs off into an orthogonal dimension for ever as planned. Well, except for Cossont who decides that actually she'd prefer to stick around, practise her sonata a bit more, hitch a lift on a Culture ship, go and visit QiRia again and have some more adventures.
Sadly there won't be any future Culture novels describing those adventures, as this was the last science fiction novel of Banks' life, published in October 2012 about eight months before his death (The Quarry was his last non-genre novel, published posthumously).
It's tremendously entertaining, as these books always are, and there are a couple of tremendously exciting action set-pieces, but to be honest it's not up there with the best of the Culture series, in my view anyway. There are a couple of reasons for this: firstly that there's too much plot involving the Culture ships with their tiresomely hilarious names and inter-ship messaging and not enough recognisably human-scale interaction. The ratio is far better than, say, Excession, which as I recall involved pretty much no organic life at all, but still. The other problem is the whole notion of Subliming - mentioned in a very hand-wavey way in several of the earlier books, it's always teetered on the edge of magic and/or religion (and aren't they, after all, pretty much the same thing) and the attempt to rationalise it here as being a sort of re-calibration of matter into a higher dimension (seventh? eighth? eh, you know, one of the spare ones) undetectable to the "real" universe feels like a bit of a cheat.
Vyr Cossont is an engaging protagonist but she doesn't really have enough to do, and, a bit like Lededje Y'breq, the nominal main character of Surface Detail, spends a lot of time being ferried around and saved from peril by a Culture ship and its AI Mind. And the endless airship party reminded me of the endless flying cocktail party in Life, The Universe and Everything - the one Arthur Dent gets hit in the small of the back by while flying - although with lots of extra body modification and freaky sex. Lastly, the central plot MacGuffin is entirely inconsequential - the big secret the Zihdren wanted to impart was that the Gzilt holy book, The Book of Truth, was, rather than being handed down from some mystical realm, a Zihdren plant as part of a sort of sociological experiment. I mean, I'm not the best person to adjudicate here, but since one of the unusual features of the Gzilt Book of Truth was that substantial portions of it did, indeed, turn out to be true, or at least consistent with how the universe behaves, it's not very clear why anyone should care. In any case the Culture Minds choose not to disseminate the information widely anyway, so no-one ever finds out.
So, obviously, completing the last Culture novel is the obvious time to construct that Culture novel top ten you've been waiting for, except that I can't, because there are only nine of them. I should preface this by saying that they are all good and contain more wit and imagination than most books of any genre, and within the sci-fi genre in particular stand out for containing humour, sex and strong female characters, none of those being things sci-fi has traditionally been very good at. So, here we go:
- Consider Phlebas
- Inversions
- Look To Windward
- Surface Detail
- Matter
- The Player Of Games
- The Hydrogen Sonata
- Use Of Weapons
- Excession
Obviously the order you read them in has a bearing; I made a point of reading them in the order they were written, so Consider Phlebas was the first one I read, and also objectively contains the most rootin'-tootin' space adventure action of all of them. That's not the sole criterion, as Inversions is pretty cerebral, although stuff does happen. Anyway, I reserve the right to change my mind about the exact order on a near-daily basis.