8 books • 3 series
Book #1: Darkness Visible
Book #1: Dirk Gently's Holistic Detective Agency: The Interconnectedness of All Kings
Book #2: Dirk Gently's Holistic Detective Agency: A Spoon Too Short
Book #3: Dirk Gently's Holistic Detective Agency: The Salmon of Doubt, Vol. 1
Book #4: Dirk Gently's Holistic Detective Agency: The Salmon of Doubt, Vol. 2