Dirk Gently's Holistic Detective Agency
Overview
Douglas Adams
Douglas Noel Adams was an English writer and dramatist. He is best known as the author of The Hitchhiker's Guide to the Galaxy, which started life in 1978 as a BBC radio comedy before developing into a "trilogy" of five books that sold over 15 million copies in his lifetime, a television...
, first published in 1987. It is described by "the author" on its cover as a "thumping good detective-ghost-horror-who dunnit-time travel-romantic-musical-comedy-epic".
The book was followed by a sequel, The Long Dark Tea-Time of the Soul
The Long Dark Tea-Time of the Soul
The Long Dark Tea-Time of the Soul is a 1988 humorous fantasy detective novel by Douglas Adams. It is the second book by Adams featuring private detective Dirk Gently, the first being Dirk Gently's Holistic Detective Agency....
. The only recurring major characters are the eponymous Gently
Dirk Gently
Dirk Gently is a fictional character created by Douglas Adams and featured in the books Dirk Gently's Holistic Detective Agency and The Long Dark Tea-Time of the Soul...
, his secretary Janice Pearce and Sergeant Gilks.
Quotations
This time there would be no witnesses. 
Chapter 1, p. 1
And time began seriously to pass.
Chapter 1, p. 3
(on sentient horses) It is difficult to be sat on all day, every day, by some other creature, without forming an opinion about them. On the other hand, it is perfectly possible to sit all day, every day, on top of another creature and not have the slightest thought about them whatsoever.
Chapter 1, p. 6