Transition is an intensely political novel. Not in the Katherine Kurtz Deryni sense, but in the sense that it was clearly written in reference to recent and ongoing real-world events. It's not subtle, but neither is it overbearing.
One of the benefits of reading (or, I can say, writing) dark fiction is that you can wake up from it with relief. Unfortunately, from the dark world of Transition, where torture and other terrible things happen, I woke to a real world where they also happen. It's a bit grim, and while the politics shouldn't put you off, the torture might - especially when you reflect that it's not just fiction - all these things are really happening. And that's from a guy who writes some dark stuff, and just finished writing a story about torture himself.
The story deals with a large cast of characters and multiple, often limited, or as the story itself points out, unreliable narrators. It takes quite some time to get a handle on what's going on, though I can reveal without spoilers that the core concept is that some people can move from their own minds into the minds of other people in alternate realities. There's a Circle organizing it all, and of course there are bad apples and power struggles (so there is some narrative politics as well).
As always with Banks, the writing is smooth. This time, however, the pieces just didn't add up to a compelling story for me. There are a number of thin or not terribly credible pieces, and a fairly substantial number of loose ends left hanging. The ending was pretty unsatisfactory.
I appreciate that Banks steered away from the Culture, which was wearing a bit thin, but this was not his best effort. True Banks fans probably already have this. If you're new to Banks or not a devotee, I suggest looking elsewhere.