4.5 stars actually. It's beautiful, poetic, tragic and sometimes sprinkled with comedy. But its already dense plot is further complicated by the way it is written: constantly shifting PoVs, so many names and characters -- it'd have been better to write chapters, longer than the paragraphs here used, focusing only on one or two characters. *Then* change the Point of View. As it is, I think that to fully appreciate it you need to read it a second time. And no, it's not because I'm a non-native English speaker.
Apart from this, it's a Magnificent Culture novel. I'm reading them all in chronological order, and I think only the very first one, Consider Phlebas shares the top spot with Excession.
Wonderful. When the boundaries between Science Fiction, Ethics and Philosophy actually disappear then you know you've got something invaluable in your hands...