It's high quality comedy from Terry Pratchett and Neil Gaiman. The base idea being that the biblical antichrist and final battle is real and approaching but the angel and demon who are meant to be leading the battle between good and evil have decided that after thousands of years on earth they're actually ok with the status quo.

It's also a TV series which was a reasonable adaptation (at least the first series, haven't watched past that) but the book is as usual superior.