A história é completamente diferente da dos livros. A página da mostra da Wikipedia é um resumo abaixo (ênfase minha):
The show is based around the eccentric Dirk Gently (Samuel Barnett) who claims to be a "holistic detective", investigating obscure cases based on the inter-connectivity of all things. During the first season he befriends Todd Brotzman (Elijah Wood) and Farah Black (Jade Eshete) who help him with his cases. Dirk's past is linked with "Project Blackwing", a secret CIA project to evaluate subjects with strange abilities. Dirk is not only followed by agents of Blackwing trying to recapture him but also by Bart Curlish (Fiona Dourif), another Blackwing subject who considers herself a "holistic assassin" and believes she is destined to kill Dirk.
Enquanto o resumo do livro começa:
Richard MacDuff attends the Coleridge dinner at his old college St Cedd's, where he witnesses his former tutor, Professor Urban "Reg" Chronotis*, perform an inexplicable magic trick in which he makes a salt cellar disappear, then reveals it by smashing a centuries-old clay pot that a young girl brought to the dinner. The dinner concludes with a reading of Coleridge's poem "Kubla Khan", including a mysterious (and fictional) second part.
Meanwhile, an Electric Monk and his horse find a mysterious door on an alien planet, which leads them to Earth. MacDuff and Prof. Chronotis find the horse in the Professor's bathroom, but this does not seem to overly surprise him. The Monk, misunderstanding a casual comment, shoots and kills MacDuff's boss Gordon Way. Way's ghost makes several attempts to contact the living.
Eu li / assisti ambos e eles são definitivamente histórias diferentes, como pode ser visto simplesmente pelos personagens envolvidos (destacado). Tudo do show é original da série, exceto Dirk e a idéia básica de sua "agência".
A @CrowTRobot mencionou que o primeiro episódio teve uma cotação fazendo referência a um sofá e a Thor, sugerindo que o programa segue os dois romances concluídos.
"Have you ever actually solved a case?"
"Sure. Tons. Well, some. Well, a few. There was a bit about a sofa, a thing with Thor..."