The back of the book has a quote from a reviewer saying "He warns you up front, this is a dark novel."
Well, compared to Banks' _The Wasp Factory_, this really isn't such a dark novel. I'll quote another reviewer from USENET who said "I can't trust an author who develops characters and kills them." This, however, is also a trait of Banks', and I cant imagine anyone would read this book expecting everyone to escape unscathed from the ominous, looming evil which permeates, quite frankly, every Banks book I've read.
The book tells a story of a woman, who becomes a metaphor for the star system she lives in. Unlike the Culture novels, the "Golter" system is at least a hundred million light years from the nearest star. They are entirely isolated. They have colonized all the planets and moons in their system, but have no hope of ever reaching anyone else. Sharrow is the same way. Alone, even while surrounded by others.
As the system society begins to attack itself, so, too, does Sharrow lose friends. Entire cities are wiped out.
This is not unexpected. You're reading a Banks novel. However, the finish of the book (as other reviewers have hinted, the last 100 pages are worth the rest of the book being somewhat slow and, well, pointless) is quite profound, and ties the rest of the story together in ways I really hadn't anticipated. It actually took me a couple days to reflect on it, and how I felt about the story he had told.
Surprisingly, after a couple days, I realized that what Banks was getting at was the good that actually came out of all the death and destruction in the book. I'll leave the reader to discover that on their own.
I'd highly recommend this to any Banks fan, but perhaps not to a first time Banks reader. Consider _Excession_ instead.