Far-future clash-of-empires yarn from the author of the Recluce fantasy series (most recently, Fall of Angels, p. 496) and The Parafaith War (1995), etc. Thousands of years ago, three types of humans lived on Old Earth: the draffs, or common people; cybs with their machine-enhanced bodies and senses; and the demis, whose godlike mental powers derived from various computer and energy nets. Following a dreadful war, the cybs were expelled. Old Earth then evolved a radically different sociopolitical system based on power and energy balances. The cybs founded various colonies, developed the Rebuilt Hegemony, and attempted to invade Old Earth, only to be blasted for their pains. Now, cybs from the Vereal Union arrive 12 two-kilometer-long spaceships built of an almost indestructible adiamante seeking revenge, conquest, or whatever technologies Old Earth has that they don't. Under Old Earth's Paradigms of Power, whoever exercises power must repay that power, usually in drudge labor, so nobody seeks to rule; a Co-ordinator must be appointed to handle the crisis. Demi Ecktor, however, must also abide by the Construct, which constrains Old Earth to do nothing until the Vereals open hostilities--the upshot being, since the cybs refuse to recognize reality, that Ecktor must choose either to sacrifice millions of demis and draffs in a needless showdown with the cybs, or allow the destruction of the only sustainable social system ever developed. Though the cybs and their lifestyle remain somewhat diffuse, this is thoughtful, persuasive, challenging, absorbing work: Modesitt's best so far.