This goes back about nine years, but I hadn’t heard the term before, and I figure I can trust Neil Gaiman’s description:
Several people asking what I meant by “Plot Coupons”.
I think Nick Lowe (the Interzone film critic, not the rock star or the Marvel editor) was the first person to coin the term. It’s a very useful way of thinking about a particular type of structure of a story.
It’s the kind of story where the protagonist(s) is told to go and collect a bunch of objects. It’s a very good way into a world, because it takes you all over, looking for things. Often, early on, someone will say something like, “A thousand years ago, Estragon The Dark Clown, for reasons that will never be adequately explained in this book or its many sequels, placed his power in The Funny Hat of Doom, The Big Red Nose of Darkness, the Wig of Desmond, and the Revolving Bow Tie of Light. It has been written, that only when these four objects come together will a Saviour arise to save Clowntown. You, Beppo, you must take this map (helpfully printed in the front of the book for easy reference) and nip around the book obtaining these four things (each the object of veneration by a different culture, each guarded by very different groups of people) at great cost to yourself and to the supporting cast, and then you must bring them back here.”
Note that “the author” can be substituted for “the Gods” in such a work: “The Gods decreed he would pursue this quest.” Right, mate. The author decreed he would pursue this quest until sufficient pages were filled to procure an advance.
Which sounds cruel, but as Nick Lowe (the rock star, not the Interzone film critic or the Marvel editor) says, you’ve gotta be cruel to be kind.