Michaelmas first appeared in the form of a two-part serial in Fantasy & Science Fiction in August and September 1976. It was published as a novel (in revised form) from Berkley Putnam in 1977, with a simultaneous British edition from Gollancz. A book club edition appeared in 1978, along with the mass-market paperback edition from Berkley. A Questar (Popular Library) paperback reprint appeared in 1986.

The novel is set in the near future (at least at the time of writing, now actually in past time).

The public image of the eponymous protagonist, Laurent Michaelmas, is that of a world-renowned newsman. In fact, Michaelmas controls world events just as much as he reports them. His means of influence is an immensely powerful self-aware artificial intelligence called Domino, which originated as a modest telephony appliance in Michaelmas' youth. Over the years, Domino has evolved into a digital omnipresence that can penetrate and control any electronic or computerized equipment, most notably communication networks of all kinds. Domino was created by Michaelmas, and its existence is known only to him.

Domino is also the confidante and intellectual sparring partner of Michelmas, compensating in part for the loss that Michaelmas suffered when his wife was killed in an accident many years ago.

By the time of the novel, Laurent Michaelmas has successfully used his power to create and sustain world peace. One of his achievements is the success of UNAC (the fictitious United Nations Astronautics Commission). Organizing space travel as a joint international project, UNAC is important to Michaelmas as a symbol of a more united world. When an astronaut believed to have been killed in a failed mission turns up miraculously saved, a threatening scenario starts to unfold. As the novel progresses, Michaelmas slowly learns that a possible extraterrestrial presence may be interfering with the new world he has worked so hard to create.

The novel is not only a fast-paced political/sci-fi thriller, but is also remarkable for its prescience, because it appeared less than a decade into the Internet era, long before its current prominence and ubiquity. The technical descriptions of near future technologies are very convincing and apparently well researched. Its description of journalism and its professional culture are likewise highly developed, mainly due to the late Budrys' residence near Northwestern University's Medill School of Journalism, which appears several times in the book.

Throughout the book, many references are made to classical works of art, theater, poetry and philosophy.

The main character, Laurent Michaelmas, bears the name of the festival honoring the Archangel Michael, a figure in Judaism that protects God's people, and in Christianity that defeats Satan in the Book of Revelation. In the novel, Michaelmas helps to protect society from itself by influencing the balances of power in the world to avoid war and maintain relative peace.

The novel incorporates features of a substantially shorter and significantly different version published in The Magazine of Fantasy & Science Fiction in 1976.

• Michaelmas title listing at the Internet Speculative Fiction Database
• Michaelmas at Open Library
• Michaelmas as serialized in The Magazine of Fantasy & Science Fiction, parts one and two, at the Internet Archive