Third in MacLeod's Engines of Light series (Dark Light, 2002, etc.). The Second Sphere lies a hundred thousand light-years in the future, colonized over millions of years and populated by descendants of terrestrial creatures: the dinosaurian saurs, the giant-squid kraken, and various hominids. Two hundred years earlier, a starship arrived from Earth; among its cosmonauts were the immortals Matt Cairns and Grigory Volkov. From a dying god, one of countless cometary intelligences composed of nanobacteria, they learned to expect an imminent invasion by non-terrestrial hostiles. Volkov makes himself dictator of planet Nova Terra, decreeing intricate space defenses capable of blasting any approaching aliens. Matt and his associates, however, go looking for the aliens and encounter them first. Far from hostile, the Multipliers eagerly join with Matt and friends; they delight in synthesizing things on a molecular level, so there will be no more need of factories or trade. Tiny Multiplier offspring can enter human bodies and rearrange genes to render everyone immortal and infuse them with a portion of the vast Multiplier racial memory. Thus are the Bright Star Cultures born. The real enemies are the crusty, ancient gods, who can't abide bustle and noise and who intended for humans and Multipliers to destroy one another. Volkov, meanwhile, blasts an unsuspecting Multiplier fleet and prepares for a showdown with Matt and the Bright Stars.
Rich, inventive, intelligent, and fascinating: so unorthodox is MacLeod that it often seems as if he's pursuing complexity as an end in itself.