The Hydrogen Sonata, by Iain with-an-M Banks @ 05:18 pm
Yep, it's a Culture novel. When I think about it, it's just something blowing up at the start, followed by a couple of long Macguffin hunts, followed by more things blowing up. Nonetheless, it's a fun jaunt around a few corners of the universe. The built-in timeline countdown as a civilization (not part of the Culture) plans to Sublime also adds to the tension as the action slowly picks up steam and hurtles toward the climax.