Excession is yet another Culture novel. I should have taken notes as I read it, because I found it confusing at the time, and now I’ve pretty much forgotten the entire plot. Wikipedia has reminded me that a mysterious alien artefact appears in space in the book, and various entities and societies vie for control (and understanding) of it. Um…yeah. If you’ve never read an Iain M. Banks book before, this probably isn’t the one to start with.