I just finished reading Transition, but Iain Banks.
It's a little bit different this one, not his usual SF style, and probably why the M is missing from his name. Transition is a lot more fantasy, set in a Multiverse where it is possible for individuals, who are Aware and have access to the drug Septum, to flit between parallel universes. Each parallel universe can be anything up to very slightly different to radically, but plausibly different, but still restricted to the Earth, or whatever it's called locally, and however the continents and nations happen to have formed.
The story is quite complex and involves many different characters, each developing in separate chapters and at least in the beginning seemingly independent. It was challenging trying to work out how they would relate, and who you should identify with, but in the end all pans out satisfactorily.
Lots of murder, assassination, torture, and sex, so that was fun.