I am about half way through Look to Windward by Iain Banks.

I find this one of the most depressing books in the Culture series as it deals with loss, grief to the point of suicide, the trauma of war lasting way beyond the war, intervention by a super power, and a rigid caste system. Its obviously heavily influenced by the Gulf War. Most of what it has to say is unlikely to be new on these topics to most readers but it does say it without being too heavy handed, most of the time.

The dirigible behemoth creatures are a delight.