After 2 brilliant novels at the beginning of his career - Revelation Space and Chasm City, Mr. Reynolds' novels became either incomplete or just showing flashes of brilliance combined with lots of forget it run of the mill action. The short stories and novellas showed an extraordinary brilliance though and I've wondered if he would ever write a novel commensurate with them
House of Suns is that novel - epic space opera on a large scale but with characters you can identify with, hard sf based on the current understanding of the limits of science and a touch of fantasy and romance to complete it. It seems that every important large scale space opera has to have some fantasy these days - as the recent works by P. Hamilton and IM Banks show, and House of Suns has a princess, an evil step-brother, wizards, magic and peasants still remaining hard sf throughout :)
Based on the Thousandth Night novella published in the 1M AD anthology, with the same universe and characters, though different action, the story takes place in a mostly human dominated Galaxy 6M years in the future, with everything allowed except causality busting - so no ftl - moving planets out of danger, Dyson spheres, cloning, intelligent robots, immortality, matter replicators, damming stars - anything conceivable today that stays within the limits of our physical understanding of the Universe is there.
Civilizations rise and fall, but towering over them are the Lines, groupings of originally 1000 immortal shatterlings though in time some are lost to attrition - all clones of a single person to start with - that have the most advanced ships, tech, and go on Circuits around the Galaxy, meeting once every 200k years to mix their memories. Of course travel being sub-light they spend most time in stasis or slow-time - they can and do slow time at will with "syncromesh", so of those 6 Million years each shatterling lived several tens of thousands - bookworms tunneling through the pages of history as they are called by entities that actually lived through millions of years though at a slow pace
The shatterlings are almost as benevolent gods to the "turnover" civilizations of the Galaxy and they trade and do good works like preventing stars to go supernova, moving planets out of harm's way...
The story focuses on 3 main characters - 2 shatterlings of the Gentian line Campion and Purslane - Campion is brash and just on the right side of censure for various actions or inactions - Purslane has the best ship of the Gentian line and is patient and determined, making a good match with her illicit lover Campion - the shatterlings are supposed to go alone on their circuits and not form bonds...
Also in small restropect chunks we get to see the original Gentian, Abigail, millions of years ago in The Golden Hour - that's a literal name - when humanity lived in the Solar system only and the shatterling project originated and some of how the Lines formed.
Purslane and Campion meeting illicitly on their way to the next Gentian reunion and preparing to falsify their memories before dumping them in the common mix, stop by an obscure planet to fix a stardam put in place to prevent a supernova extinction of the local civilization.
Being late to the meeting, they detour to fix Campion's ship, and in the process rescue a strange robot of the machine people - Hesperus - with missing memories. Finally on their way to the reunion, they get a very disturbing message and the adventure begins...
The ending is fulfilling, leaving space for a sequel if the author desires but completing the story very nicely.