Book — House of Suns by Alastair Reynolds

Pretty, but ultimately hollow Big Dumb Object/Sense of Wonder stuff, set in the (post)human-filled galaxy of 6 Myr hence. Suffers from chunks of idiot plotting (when you're fleeing from a massacre, and suspect a traitor in your midst -- identity easily spotted by someone who never manages to get ahead of the detective in a whodunnit -- you don't leave the person working on reverse engineering the answer to why this is all going on to work in solitude, you get them broadcasting every step of the work), and from needlessly firing off all the Chekov guns at the end for a totally flat finale.

Really, in a big-scope SF story, it's better if some of the wallpaper just stays that way, as odd local colour to make the setting distinct from any other, rather than having to become a plot point.