Dirk Gently's Holistic Detective Agency
Douglas Adams
HHGTTG - The Lost Chapters
The hitchhiker's guide to the galaxy
Last Chance to See
Life, the Universe and Everything
The long dark tea-time of the soul
Mostly harmless
The Restaurant at the end of the universe
The Salmon of Doubt
So Long, and Thanks for All the Fish
The Ultimate Hitchhiker's Guide - All Six Books
Young Zaphod Plays It Safe