My first Alastair Reynolds novel, I found this to be a pretty good stand-alone space opera that avoids some of the usual tropes of the genre. Humans are alone in the galaxy -- the many civilizations populating the galaxy are far future posthumans evolved from the original human race. There is no FTL travel; humans spend literally hundreds of thousands of years touring the galaxy in sub-light ships of immense size.
House of Suns begins with an attempt to wipe out the Gentian line by mysterious attackers. The search for the identity and motives of their adversaries leads to the uncovering of a conspiracy that is literally millions of years old.
It has a great epic scope (millions of years, thousands of light years), but the characters themselves never really interested me much, and the rise and fall of interstellar civilizations failed to catch me up in an epic sweep of events -- instead, the finale is a long, long starship chase.
I enjoyed it quite a bit, and will probably try something else by Reynolds, but it didn't quite hit the "Wow" level for me.