Look to Windward
By Iain M. Banks
I read this a few weeks ago now but not managed to post about it. This was another very good Culture novel; one of the best I've read. Banks seems to get better as he wrote the series.
This book covers pain and loss of war, and the morality of revenge. All told from a very Banks viewpoint, with characters not always all they seem and technology of the "magic" variety (so high it seems like magic, per Arthur C Clarke's famous quote). A wonderful addition to the Culture universe with a beautiful and bittersweet resolution.