Heroquest (no, not HeroQuest, which I would have preferred) I came up with the idea of four round-robin narrators vaguely inspired by Jack Vance, Bret Easton Ellis, the Beowulf poet, and Terry Pratchett respectively. And before you raise a very legitimate objection, I did say vaguely.
I don't recall there being a Heroquest world at the time I wrote the first book, so I created part of one and drew my own map of it. By the time I was asked to write the second book, Games Workshop had designed their own version of the world, which included some of the place names from my novella but with a quite different geography "loosely based on the Warhammer world" as it said in the front. I just mention that because if you refer to the map from the second book while reading the first, you will see that the route the characters take makes no sense. One view at the time was, "Well, it's for ten-year-olds," but I can tell you that when I was ten that sort of thing would've annoyed the hell out of me.
As well as the novella, the book The Fellowship of Four included a mini-gamebook, "In the Night Season", and that's this year's Christmas freebie. Grab it now here while stocks last.
Somebody also created an actual HeroQuest set-up based on the novella, here. And while we're about it, an early Christmas freebie was the second Heroquest book, The Screaming Spectre, and if you missed that 'tis the season to be jolly all over again, here.