According to The Nice and Accurate Prophecies of Agnes Nutter, Witch (the world's only completely accurate book of prophecies, written in 1655, before she exploded), the world will end on a Saturday. Next Saturday, in fact. Just before dinner. So the armies of Good and Evil are amassing, Atlantis is rising, frogs are falling, tempers are flaring. Everything appears to be going according to Divine Plan. Except a somewhat fussy angel and a fast-living demon—both of whom have lived amongst Earth's mortals since The Beginning and have grown rather fond of the lifestyle—are not actually looking forward to the coming Rapture. And someone seems to have misplaced the Antichrist . . .

It is the coming of the End Times: the Apocalypse is near, and Final Judgment will soon descend upon the human race. This comes as a bit of bad news to the angel Aziraphale (who was the angel of the Garden of Eden) and the demon Crowley (who, when he was originally named Crawly, was the serpent who tempted Eve to eat the apple), respectively the representatives of God and Satan on Earth, as they have become used to living their cozy, comfortable lives and have, in a perverse way, taken a liking to humanity. As such, since they are good friends (despite ostensibly representing the polar opposites of Good and Evil), they decide to work together and keep an eye on the Antichrist, destined to be the son of a prominent American diplomat stationed in Britain, and thus ensure he grows up in a way that means he can never decide between Good and Evil, thereby postponing the end of the world.

Unfortunately, Warlock, the child everyone thinks is the Anti-Christ is, in fact, a perfectly normal eleven-year-old boy. Due to mishandling of several infants in the hospital, the real Anti-Christ is Adam Young, a charismatic and slightly otherworldly eleven-year-old who, despite being the harbinger of the Apocalypse, has lived a perfectly normal life as the son of typical English parents and as a result has no idea of his true powers. As Adam blissfully and naively uses his powers, creating around him the world of Just William (because he thinks that is what an English child's life should be like), the race is on to find him—the Four Horsemen of the Apocalypse assemble and the incredibly accurate (yet so highly specific as to be useless) prophecies of Agnes Nutter, seventeenth-century prophetess, are rapidly coming true.

Agnes Nutter was a witch in the 17th century and the only truly accurate prophet to have ever lived. She wrote a book called The Nice and Accurate Prophecies of Agnes Nutter, Witch, a collection of prophecies that did not sell very well because they were unspectacular, cryptic and, ironically enough, all true. She, in fact, decided to publish it only so that she could receive a free author's copy. There is only one copy of the book left, which belongs to her descendant Anathema Device. Agnes was burned at the stake by a mob (because that is what mobs did at that time); however, because she had foreseen her fiery end ("Ye're tardy; I should have been aflame ten minutes since") and had packed 80 pounds of gunpowder and 40 pounds of roofing nails into her petticoats, everyone who participated in the burning was killed instantly.

Anathema teams up with Newton Pulsifer, the descendant of the man who initiated the burning of Agnes, to use the prophesies and find the Antichrist. Unfortunately, that is exactly what everyone else is trying to do, and time is running out.

Sir Terence David John "Terry" Pratchett, OBE (born 28 April 1948) is an English novelist, known for his frequently comical work in the fantasy genre. He is best known for his popular and long-running Discworld series of comic fantasy novels. Pratchett's first novel, The Carpet People, was published in 1971, and since his first Discworld novel (The Colour of Magic) was published in 1983, he has written two books a year on average. His latest Discworld book, Snuff is the third-fastest-selling novel since records began in the United Kingdom selling 55,000 copies in the first three days.

Pratchett was the UK's best-selling author of the 1990s, and as of August 2010 had sold over 65 million books worldwide in thirty-seven languages. He is currently the second most-read writer in the UK, and seventh most-read non-US author in the US.

Pratchett was appointed Officer of the Order of the British Empire (OBE) "for services to literature" in 1998. In addition, he was knighted in the 2009 New Year Honours. In 2001 he won the Carnegie Medal for his young adult novel The Amazing Maurice and his Educated Rodents.

In December 2007, Pratchett publicly announced that he was suffering from early-onset Alzheimer's disease and, subsequently, made a substantial public donation to the Alzheimer's Research Trust, and filmed a programme chronicling his experiences with the disease for the BBC.

Neil Richard Gaiman ( /ˈɡeɪmən/; born 10 November 1960) is an English author of short fiction, novels, comic books, graphic novels, audio theatre and films. His notable works include the comic book series The Sandman and novels Stardust, American Gods, Coraline, and The Graveyard Book. Gaiman's writing has won numerous awards, including Hugo, Nebula, and Bram Stoker, as well as the 2009 Newbery Medal and 2010 Carnegie Medal in Literature. He is the first author to win both the Newbery and the Carnegie medals for the same work.

Gaiman and Pratchett had known each other since 1985 and it was their own idea, not that of their publisher, to collaborate on a novel.

Neil Gaiman has said:

We were both living in England when we wrote it. At an educated guess, although neither of us ever counted, Terry probably wrote around 60,000 "raw" and I wrote 45,000 "raw" words of Good Omens, with, on the whole, Terry taking more of the plot with Adam and the Them in, and me doing more of the stuff that was slightly more tangential to the story, except that broke down pretty quickly and when we got towards the end we swapped characters so that we'd both written everyone by the time it was done, but then we also rewrote and footnoted each others bits as we went along, and rolled up our sleeves to take the first draft to the second (quite a lot of words), and, by the end of it, neither of us was entirely certain who had written what. It was indeed plotted in long daily phone calls, and we would post floppy disks (and this was back in 1988 when floppy disks really were pretty darn floppy) back and forth.

while Terry Pratchett has said:

I think this is an honest account of the process of writing Good Omens. It was fairly easy to keep track of because of the way we sent discs to one another, and because I was Keeper of the Official Master Copy I can say that I wrote a bit over two thirds of Good Omens. However, we were on the phone to each other every day, at least once. If you have an idea during a brainstorming session with another guy, whose idea is it? One guy goes and writes 2,000 words after thirty minutes on the phone, what exactly is the process that's happening? I did most of the physical writing because:

I had to. Neil had to keep Sandman going – I could take time off from the DW;

One person has to be overall editor, and do all the stitching and filling and slicing and, as I've said before, it was me by agreement – if it had been a graphic novel, it would have been Neil taking the chair for exactly the same reasons it was me for a novel;

I'm a selfish bastard and tried to write ahead to get to the good bits before Neil.

Initially, I did most of Adam and the Them and Neil did most of the Four Horsemen, and everything else kind of got done by whoever – by the end, large sections were being done by a composite creature called Terryandneil, whoever was actually hitting the keys. By agreement, I am allowed to say that Agnes Nutter, her life and death, was completely and utterly mine. And Neil proudly claims responsibility for the maggots. Neil's had a major influence on the opening scenes, me on the ending. In the end, it was this book done by two guys, who shared the money equally and did it for fun and wouldn't do it again for a big clock."