For those who are unfamiliar, this is Douglas Adams famously unfinished doctor who episode.

Seeing as it was unlikely to ever be released, Adams recycled the plot in to his novel Dirk Gently's holistic detective agency, replacing the doctor with the titular gently (and effectively making Dirk gently doctor who fan fic)

Then it was rereleased as a radio episode and a flash animation, and a fan novel, and a recut fanedit, and a VHS with linking narration, and an official novel, and now this.