To date, the corpus of the Alliance–Union universe consists of 27 science fiction novels along with a series of seven short story anthologies edited by Cherryh and a few other miscellaneous works.
Patricia Monk suggested in her paper "The shared universe: an experiment in speculative fiction" that linking these Alliance–Union series in a common future history creates a "megatext" or "collage novel".
[4] As humanity reaches out to the stars, space stations are financed by the private Sol Corporation, eventually renamed the Earth Company.
The stationers and the merchanters who man the ships that supply them both develop distinct cultural identities, but remain psychologically and to some degree materially dependent on Earth.
With a poor understanding of stationers and merchanters alike, its clumsy attempts backfire, provoking first unrest, then occasional armed clashes, and eventually rebellion.
The situation culminates in 2300 with the declaration of an independent Union by the colonists centered at the Cyteen system, another habitable planet and space station at Lalande 46650, precipitating outright war.
Union augments its population and armed forces with genetically engineered and psychologically conditioned human clones, called azi, which are seen as an abomination by Earth.
With sporadic, inadequate support from Earth, the Fleet has no choice but to forcibly requisition equipment and personnel from the increasingly alienated merchanters.
Faced with the increasingly dangerous situation, many of the merchanter families finally band together to form the Alliance, creating a third, neutral power, soon after a team arrives from Earth to negotiate an end to the conflict.
When Signy Mallory, one of his most senior captains, learns of his plans to seize control of Earth itself, she and her ship, Norway, defect to the new Alliance, becoming the core of its militia.
Because Union does not dare weaken its forces at this crucial juncture to guard its rear against the newborn state, the Alliance is able to broker a favorable peace treaty, with Pell Station as its de facto home base.
The treaty cedes to the Alliance a monopoly on interstellar commerce, even within Union, giving it the power to shut down stations simply by withholding trade.
The Merovingen Nights series takes place on a single planet and features swashbuckling heroes and low levels of technology, and as such might be classified as science fantasy, borrowing elements from the historic sword and planet subgenre; this is also true for the Morgaine Cycle books, set remotely in time and space from the main sequence.
The first exception she notes is the two novels Heavy Time and Hellburner, which should be read in that order (as originally published and as compiled together in the omnibus edition Devil to the Belt).
It was the discovery of sentient life that sent shock waves back to Earth, sparking off moral, religious, philosophical and policy debates.
Gehenna is a rare habitable Alliance–Union universe planet in the Zeta Reticuli system, and home to the calibans, sentient lizard-like creatures.
Planet Merovin is isolated, forsaken by the rest of humanity because of poor interstellar relations with an aggressive alien species, the Sharrh.
This process is the result of deliberate social engineering on the part of Reseune, the Cyteen-based center of all research and development concerning human cloning.
The Mazianni is a term which refers to the military star-ships and their crews who remain loyal to their commander, the charismatic, ambitious Conrad Mazian, when he renounces his allegiance to Earth.
Downbelow Station ends with his (implied) failure, and the defection of one of his most senior captains, Signy Mallory, and her ship Norway to the newborn Merchanter's Alliance, based at Pell.
[1] Writing in The Encyclopedia of Science Fiction, Clute added that while the universe's structure is "rough at the edges", reading a novel in the series creates the impression that it is part of a larger history yet to be revealed.
[1] In a biography of Cherryh in the Historical Dictionary of Science Fiction in Literature, M. Keith Booker described the Alliance–Union universe as "so far-reaching that its overall outlines remain unclear and continue to develop".