Dirk Gently is a series of two novels written by Douglas Adams, featuring the "holistic" detective Dirk Gently. The titles are:
• Dirk Gently's Holistic Detective Agency
• The Long Dark Tea-Time of the Soul
He had begun a third book in the series titled "The Salmon of Doubt" but died before completing it. The unfinished novel was published in 2002 as part of "The Salmon of Doubt: Hitchhiking the Galaxy One Last Time" which is a posthumous collection of previously published and unpublished material by Douglas Adams.