The show is based on the book Good Omens: The Nice and Accurate Prophecies of Agnes Nutter, Witch. It was written by Terry Pratchett and Neil Gaiman and it kind of reads like Monty Python or the Hitchhiker’s Guide…very funny…very British.
Here’s a little info on the premise of the book:
The world will end on Saturday. Next Saturday. Just before dinner, according to The Nice and Accurate Prophecies of Agnes Nutter, Witch, the world’s only completely accurate book of prophecies written in 1655. The armies of Good and Evil are amassing and everything appears to be going according to Divine Plan. Except that a somewhat fussy angel (Aziraphale) and a fast-living demon (Crowley) are not actually looking forward to the coming Rapture. So, they attempt to sabotage it because they like their comfy lived in merry old England. And someone seems to have misplaced the Antichrist and then there is the issue of the Four Horsemen.
I suggest that if you are looking forward to the show, give the book a shot. You will not regret it!