In an interview I read a while back, Iain Banks said he'd be releasing his literary fiction under "Iain M. Banks" in the US, because the middle initialed-name (which he normally uses for his science fiction) sells better here. The first book published this way is Transition. What he doesn't add is that it's been a long time since Banks's work has been sold here at all, regardless of genre. That fact only really started to change with the publication of his previous book, Matter, and Orbit's subsequent reissues of his older titles.
I don't remember ever discussing Matter at length here, but it serves as a useful contrast with Transition, and not just because they're ostensibly different genres (Transition has a lot of sci-fi elements, but uses them very lightly). They're also vastly different in scale and technique, representing the two poles of Banks's work.
The seventh Culture novel, Matter's primary theme is interference and intervention by outside powers. It concerns members of the royal family in a medieval society surrounded by far more intelligent aliens, including the Culture. When the kingdom is manipulated into civil war, the family's dim oldest prince has to go on the run, aided by his sister, who left the planet as a child to become a Culture agent. Along the way, Banks visits a typically-diverse cast of hyper-paranoid spies, eccentric drones, and nearly incomprehensible alien societies. The characterization is also superb--Prince Ferbin is either hilariously unaware or scornful of the opportunities that the galaxy has to offer, while his servant Choubris becomes increasingly independent as he sees a society beyond their feudalistic home, eventually inverting their relationship entirely.
A lot of people seem to have found Matter to be dense and a bit depressing, but it's actually one of my favorite books from the Culture set. Part of the joy of the series is the enthusiasm that Banks shows for huge ideas and massive pyrotechnics: there's no particular reason that the climax of the book has to take place in the den of the enormous alien creature living at the core of an artificial shellworld, but it's a lot of fun. That goes for the book's philosophy as well--the Culture is itself one of the those big, unrealistic ideas (it's a technocratic, post-scarcity socialist utopia run by AIs), as is Matter's flirtation with intergalactic interventionism. Banks delights in setting up his ideals, then finding ways to knock holes in them, as with the Culture's euphemistically-named spy division Special Circumstances, or Matter's ultimately ambivalent parallels to neo-conservative foreign policy.
Transition, on the other hand, is much lighter fare. It's told from multiple perspectives, some of which are not identified by name until late in the text. Most of the time is spent with four characters: a reluctant assassin, a torturer known as "The Philosopher," an ambitious young hedge fund manager, and a hospital patient recovering from amnesia. The story spans parallel universes, as several characters are members of a secret society able to hop between possible realities using a drug called "septus," which deposits them in the bodies of people at their destination.
The "transition" of the title thus refers partly to the process of moving from world to world. But it's also a reference to the primary theme of the book, which is the struggle between progress and stasis, as The Concern (the secret society controlling access to septus) teeters between one faction that would preserve the status quo (including giving immortality to members of its ruling council) and another in favor of actively encouraging diversity of thought and outcome across worlds.
Where Matter spent a lot of time in the grey areas of its theme, Transition is far more straightforward. The challenge in reading it comes more from deciphering how the various perspectives fit together, particularly the hospital patient, who may or may not be the same as one of the other characters. It reminded me strongly of The Bridge, one of Banks's earliest books, which also experimented with mixing different voices, perspectives, and shifts in genre. This is skillful and playful writing, but it doesn't stick with me the way that Matter does.
But this is all nitpicking: they're both great books, and I'm thrilled that they're being sold here, middle initial or no. They're not the titles I'd pick as an intro to Banks (that'd be Player of Games on the Culture side, and either Whit or The Bridge from the literary fiction), but they're solid works from a mature and interesting writer. Both come highly recommended.