Rather unusually, considering the often dark nature of the television series, the novelisations based on episodes were all aimed at the "Young Adult" market. However, of the 201 episodes produced, these novelisations only covered 27 of them.

Anyone attempting to collect every single X-Files novelisation should also be aware of a series of six licensed books which started out as behind-the-scenes reference books, and which eventually transformed into a series of extremely detailed collections of plot synopses that included much of the dialogue from each episode.

The first two books were The Truth is Out There and Trust No One, and it is these two volumes which include the majority of the behind-the-scenes information. I Want to Believe was the first volume to contain the in-depth synopses and covered Season Four. Each episode synopsis took up between 10-14 pages and also included details of the cast, settings, brief episode credits and a smattering of facts about the episode in question. Resist or Serve and The End and the Beginning covered all of the episodes from Seasons Five and Six (although bizarrely not the movie Fight the Future), with the final volume being All Things, which covered Season Seven.

Further details of the six books can be found on the X-Files: Introduction page.