As a long time Iain M. Banks fan I must admit I have been a bit disappointed with some of his latest stuff. For example Surface Detail and Matter, while good reads, left me feeling like maybe the prime had been passed. So I didn't have huge expectations for this latest Culture novel. However I was very relieved to find that The Hydrogen Sonata was what might be described on a back cover as a rip-roaring return to form for this master of whatever it is he does when he writes a good Culture Novel.
In Short, if you loved 'Excession' and 'Look to Windward', if you love the way Mr. Banks can craft a single paragraph that somehow manages to take the plot forward, deepen the mystery, enrich the characters and be an elaborately crafted joke while commenting on the contrasts between The society of the Culture and our own, then don't be afraid to go into this book with high expectations.
....Well, I liked it anyway.