The apocalypse is here! Except there's been a hitch, we've lost the Antichrist. Now it's up to the forces of good, evil, and humanity to find him and avert the coming apocalypse. Good Omens by Terry Pratchett and Neil Gaiman is a lot of things. It's got a great and strange buddy story between an Angel and a Demon, it's got a love story between a hapless Witchhunter and a too psychic than must be good for her Witch, and it's a coming of age story. It's also another hilarious look at humanity, and how human nature can be both better than angelic nature and worse than demonic.
First we have our buddies Aziraphale, and angel, and Crowley, a demon. These two have been on earth fighting the forces of heaven and hell by meddling with humanity for a few millennium. In fact they have been doing this so long that they both have found out that they might like humans a little. Therefore when Crowley is called upon to start the ball of the apocalypse rolling the first person he tells is his buddy the angel. So they hatch a plan to influence the child both angelically and demonly so that the end result is basically normal.
Only problem is somewhere in there they've lost the real Antichrist. There was a small communications hitch at the hospital where he was dropped off, and he could be anywhere.
Enter Anathema Device, Witch. She has the only book ever written that has only true prophecy in it. She's followed it's advice and gone to a small village outside London to find the end of the world. Thing is, so has Witchfinder private Newt Pulsifer. (One of two remaining members of the Witchfinder army) Not because he knows the end is nigh, but because the town has some rather odd weather patterns. It's fated that they shall meet and at least bump uglies, if not fall in love.
Then there's Adam and the Them. A gang of small children with huge imaginations, huge ideas, and little devil in all of them. Although, there's a lot of the devil in Adam. You see, he's the lost Antichrist who has been allowed to grow up human.
In the end, The apocalypse is thwarted not by heaven or hell, but by a boy with power that was allowed to grow up without the influence of heaven or hell. He grows up human incarnate, and at 11 years old has too much to see and do to end the world. Plus it would be dead boring if you didn't have a few amiable enemies about to fight. Maybe you would turn on each other.
What makes this a great book is that it tones down Pratchett's Monty Pythonesque writing style, and tones up the darkness that Gaiman is known for. Also it takes a look at how maybe in the end despite the better plans of heaven and hell the apocalypse isn't thwarted by some sort of hero, but by human error, human love, and human imagination.