Good Omens is a comedic novel by Terry Pratchett and Neil Gaiman. The plot focuses primarily on the attempts of Heaven and Hell to bring about the Apocalypse and the efforts of two characters—an angel named Aziraphale and a demon named Crowley—to thwart such attempts. Aziraphale and Crowley have both lived among humans for several thousand years and have grown fond of humanity and their lives on Earth. Therefore, despite representing opposing divine parties, the two know each other well and interact often—to Crowley, Aziraphale is “an enemy for six thousand years now, which made him sort of a friend.
It is also because of their common fondness for Earth and the human race that the two work together to prevent the coming of the End Times. Their collaboration results in the planning and execution of comically ridiculous schemes: most notably, the plan to switch the son of Satan (a.k.a the Antichrist) with another, normal baby to hinder the role Satan’s son was meant to play in bringing about the Apocalypse.
Good Omens presents the stories of many other characters as well. After the execution of Aziraphale and Crowley’s scheme to switch the babies, the novel continues to follow the story of the son of Satan—Adam Young—as he grows up with a group of normal children and a normal family. Adam ends up developing and realizing his divine powers nevertheless, which causes a series of events essential to the conclusion of the novel.
Also involved are the Apocalyptic Horsepersons: War, Famine, Pollution, and Death. The Horsepersons join together in the form of an apocalyptic motorcycle gang and work to bring about the Apocalypse by bringing chaos to humanity in the forms their names represent. While they do not owe their allegiance to Heaven nor Hell, they are intended by both divine parties to be the means through which the End Times will be initiated.
The story of Anathema Device and Newt Pulsifer is another major plot arc in the novel. Anathema is a descendant of a witch named Agnes Nutter, and organizes her life around a book by her ancestor called “The Nice and Accurate Prophecies of Agnes Nutter, Witch.” The book contains detailed predictions about the End Times which Anathema believes wholeheartedly. She later encounters Newt Pulsifer, a descendant of witchfinder Thou-Shalt-Not-Commit-Adultery Pulsifer, when he crashes his car and she brings him into her cottage until he regains consciousness. The two remain together and collaborate over the course of the rest of the novel, developing a romantic interest in each other.