GOOD OMENS

The Nice and Accurate Prophecies of Agnes Nutter, Witch

By Neil Gaiman and Terry Pratchett

Workman. 354 pp. $18.95

That old Manichaean duality has been with us a long time, longer even than science fiction. Questions of Good versus Evil (or Good and Evil, or Misdirection and Righteousness) have come up again and again, producing some classics (and lots of clunkers) in the genre.

In "Good Omens," Neil Gaiman and Terry Pratchett have gone back to the original: Heaven versus Hell as acted out in the Book of Daniel and the Revelation of St. John. The result is something like what would have happened if Thomas Pynchon, Tom Robbins and Don DeLillo had collaborated on the screenplay of a remake of the Jack Benny film "The Horn Blows at Midnight," which is about an angel sent to Earth to destroy the planet with Gabriel's horn.

We start out following Aziraphale, the angel who used to hold the flaming sword outside the gates of Eden and who now runs a used-book store, and Crowley, who used to be the serpent and who now drives a Bentley, in a couple of conversations. Through the millennia, they've come to some kind of accommodation as rival businessmen. They've also both grown fond of mankind.

Then Crowley's given the job of taking the baby Antichrist to the hospital where the satanist nuns are to make the switcheroo with a normal healthy baby. This is all just a setup. About Page 38, the book shifts gears and goes from what could have been just another yuk-filled fantasy novel into something that's a whole lot better than that. And the book does this two or three more times, until it becomes a real book about real people and things, and goes beyond genre concerns entirely, while retaining the trappings.

Things go wrong from the hospital scenes onward for the two supernatural beings: The writers do that job so well that neither the reader nor the characters realize what's wrong until 11 years into the narrative.

Also gumming up the Armageddon works is someone who's been dead 300 years. The book is subtitled "The Nice and Accurate Prophecies of Agnes Nutter, Witch," the "nice" being the old meaning of "exact and precise." That's also the title of Agnes's book of revelations -- she saw the future exactly as it would happen, the only thing wrong was that she couldn't quite understand the context in which future events happened; cars seemed to be chariots, skyscrapers towers and so on. Otherwise she was right on the money. Agnes's book is in the hands of the last of her line of descendants, Anathema Device, also a witch, but a modern one who lives in a bungalow called Jasmine Cottage and who rides a bicycle and can use a theodolite.

There are also the last two soldiers in the Witchfinders' Army, Sergeant Shadwell and Private Pulsifer, still keeping the Puritan ideals alive as well as possible, armed with firelighters and pins. There are the Four Bikers of the Apocalypse (the scenes devoted to them in their pre-Apocalyptic days are the best writing in the book), a Hound from Hell that seems for one second a gift gerbil in a cage, a set of perfectly normal kids (the Antichrist's playmates), a cast of supporting and thwarting demons and angels, lots of literary inventiveness in the plotting and chunks of very good writing and characterization.

There are, of course, problems. First, the writers have set themselves the almost impossible goal of being funny about Armageddon without writing a stupid book. Second, some of the humor strains for effect -- it's genre funny. Fortunately, there's not much of that here -- but the authors can write so well it's like biting down on tinfoil when it happens.

Besides the hard job of getting the Apocalypse right, there's that old Unknown Magazine bugaboo of having true supernatural beings operant in a technological world, depending on that technology for transport and communication. This is one of those plots in which everybody must be at the same place at the same time. What we get are various humans and beings arriving by whatever means -- Bentley, bicycle, motorcycle -- when what we've had from a couple of protagonists a few pages before is a 20-mile chase through a telephone as disincorporated electrons.

All this aside, the book tackles things most science fiction and fantasy writers never think about, much less write. It does it in a straightforward manner. It's about Predestination and Free Will, about chaos and order, about human beings, their technology and their belief systems.

When the book is talking about the big questions, it's a wow. It leaves room in both the plot and the reader's reactions for the characters to move around in and do unexpected but very human things.

It would make one hell of a movie.

Or a heavenly one. Take your pick.

That's what the characters have to do.

The reviewer's latest short-story collection is "Night of the Cooters: More Neat Stories."