Question: Which book, which is described by the author on its cover as a "thumping good detective-ghost-horror-who dunnit-time travel-romantic-musical-comedy-epic, was turned into a comic science fiction television series called Dirk Gently?

Context articles: Caroline Cave
Dirk Gently's Holistic Detective Agency
Dirk Gently (TV series)
Pilot (Dirk Gently)
Fiona Dourif
Jamie Mathieson
Billy Boyle
Samuel Barnett (actor)
Hannah Marks
Max Landis

Caroline Cave is a Canadian film, television and stage actor, known for her roles in the films "This Beautiful City", "One Week", "The War Bride" and "Saw VI", and the television series "Cra$h & Burn".
 She has also had guest roles in "The L Word", "Haven", "Stargate Atlantis", "Kevin Hill", "The Associates", "Dirk Gently's Holistic Detective Agency", and "Die neue Prophezeiung der Maya (End of the World) 2013.
 She recently co-starred in the 2015 Lifetime TV movie Accidental Obsession.
Dirk Gently's Holistic Detective Agency is a humorous detective novel by Douglas Adams, 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".
Dirk Gently is a British comic science fiction detective television series based on characters from the novel "Dirk Gently's Holistic Detective Agency" by Douglas Adams.
 The series was created by Howard Overman and stars Stephen Mangan as holistic detective Dirk Gently and Darren Boyd as his sidekick Richard MacDuff.
 Recurring actors include Helen Baxendale as MacDuff's girlfriend Susan Harmison, Jason Watkins as Dirk's nemesis DI Gilks and Lisa Jackson as Dirk's receptionist Janice Pearce.
 Unlike most detective series "Dirk Gently" features broadly comic touches and even some science fiction themes such as time travel and artificial intelligence.
The pilot episode of Dirk Gently is the first broadcast episode of the BBC Four television series inspired by Douglas Adams's novel "Dirk Gently's Holistic Detective Agency".
 First broadcast on 16 December 2010 and repeated throughout the Christmas period, it was written by Howard Overman and stars Stephen Mangan as holistic detective Dirk Gently and Darren Boyd as his sidekick Richard Macduff.
 Recurring actors include Helen Baxendale as Susan Harmison, Jason Watkins as DI Gilks and Lisa Jackson as Janice Pearce.
Fiona Dourif (born October 30, 1981) is an American actress.
 She is best known for her role as Nica Pierce in two films from the "Child's Play" franchise, "Curse of Chucky" (2013) and "Cult of Chucky" (to be released late in 2017).
 Dourif's other film roles include "Fear Clinic" (2014) and "Gutshot Straight" (2014).
 Dourif is also known for her roles as Bart Curlish in the television series "Dirk Gently's Holistic Detective Agency" and Casey in "True Blood".
Jamie Mathieson is a British television writer.
 A former stand-up comedian, he has written for a number of UK science fiction TV shows, namely "Being Human", "Dirk Gently", and for series 8, 9 and 10 of "Doctor Who".
 He also scripted the 2009 film "Frequently Asked Questions About Time Travel".
 He wrote the drama pilot "ALT" for Channel 4 in 2014.
 It was announced in October 2014 that Mathieson will be the lead writer of French science fiction series "Métal Hurlant: Origins," a sequel to "Métal Hurlant Chronicles", which is currently in development.
Billy Boyle is an Irish actor on British film, television and stage.
 He is a veteran of the West End stage having played leading roles in over 15 hit shows.
 In his first West End musical "Maggie May" he was nominated as best newcomer.
 Gower Champion then chose him to play Barnaby in "Hello Dolly" at The Theatre Royal Drury Lane.
 He appeared in "Canterbury Tales" at the Phoenix Theatre as The Clerk of Oxford.
 Harold Hobson, The Times critic said, "He was a breath of fresh air in the West-End".
 He then went on to play leading roles in "No Sex Please, We're British", "Billy", "What's a Nice Country", "The Rivals", "Love, Lust, & Marriage", "Some Like it Hot", Disney's "Beauty and the Beast", and in the original cast of "Dirty Dancing.
 Lately he has appeared as Grandpa George" and Grandpa Joe in Charlie and The Chocolate Factory at Drury Lane.
 In 2016 he was Major Bouvier and Norman Vincent Peale in the smash hit Grey Gardens.
 He followed this playing Arvide in Guys and Dolls at the Phoenix Theatre in the West End.He has had his own very successful television series in Ireland "It's Billy Boyle" as well as leading roles in "Trail of Guilt", the award-winning "The Grass Arena", "The Bretts", as well as many guest appearances in EastEnders, The Professionals, Coronation Street, Father Ted etc.
 In the late 1970s, Boyle was cast as 'Ronald McDonald' in the European TV commercials and in all print media for the fast food chain McDonald's.
 He was the last 'straight man' to Basil Brush on BBC1's "The Basil Brush Show" and later presented a programme, Dance Crazy for ITV, on the history of dance with Lesley Judd.
 Lately he has been seen in Dirk Gently, for BBC Four and Lead Balloon.
 His many films include Stanley Kubrick's "Barry Lyndon", "Groupie Girl", "Side by Side", "Shergar", "Wild Geese II", "The Scarlet and the Black", "Round Ireland with a Fridge" and A United Kingdom.
Samuel Barnett (born 25 April 1980) is an English actor.
 He has performed on stage, film, television and radio, and achieved recognition for his work on the stage and film versions of "The History Boys" by Alan Bennett.
 His television performances include roles in the BBC comedy "Twenty Twelve" and in the Showtime drama "Penny Dreadful".
 On 29 March 2016 it was announced that he had been cast as Dirk Gently in the BBC America adaptation of the "Dirk Gently's Holistic Detective Agency" book series by Douglas Adams.
Hannah Gayle Marks (born April 13, 1993) is an American television and film actress.
 She best known for her role on the television series "Dirk Gently's Holistic Detective Agency".
Max Landis (born August 3, 1985) is an American screenwriter, director, producer and comic book writer who wrote the films "Chronicle" (2012), "American Ultra" (2015), and "Victor Frankenstein" (2015), as well as a variety of short films including "The Death and Return of Superman" and "Wrestling Isn't Wrestling".
 Recently, he has acted as an executive producer on the Syfy anthology horror series "Channel Zero", as well as creator and showrunner for the American adaptation of Douglas Adams' science fiction detective comedy novel series "Dirk Gently's Holistic Detective Agency" on BBC America, which both premiered in October 2016.