Dirk Gently (also known by a number of other names, including Svlad Cjelli), the operator of the eponymous detective agency that operates based on the "fundamental interconnectedness of all things." He specialises in missing cats and messy divorces. At university, Dirk, seemingly deliberately, created rumours about having clairvoyant abilities by vigorously denying that he had any. He concocted a "get-rich scheme" offering a university exam preparation service and was eventually sent to prison when, by sheer coincidence, he accurately duplicated the exam papers for that year without having seen them.
Richard MacDuff, a young software engineer working for WayForward Technologies II, owned by Gordon Way. His Anthem software, which is designed as a spreadsheet, but also has a unique feature to convert corporate accounts into music, was extremely popular, but he is falling behind in his deadlines to create an updated version. Throughout the book, he tries to figure out how a couch became impossibly stuck in the L-shaped stairway to his flat, forcing him and any visitors to climb over it to get to his flat.
Reg (Professor Urban Chronotis, the Regius Professor of Chronology), Richard's old college tutor, a fellow of St. Cedd's College, Cambridge with no apparent duties, who is "on the older side of completely indeterminate". He has a predisposition for childish conjuring tricks and an extremely bad memory.
Gordon Way, the owner of WayForward, who is pressuring Richard to complete his behind-schedule software project, and ends up getting shot for no immediately obvious reason a few chapters into the book.
Susan Way, sister of Gordon Way and professional cellist, and the "specific girl that Richard is not married to".
An Electric Monk from a planet very far from the Earth. Electric monks are coincidentally humanoid robots designed to practice religion in their owners' stead. This particular monk had accidentally been connected to a video recorder and, in attempting to believe everything on the TV, had malfunctioned and begun to believe "all kinds of things, more or less at random", including things like tables being hermaphrodites and God wanting a lot of money sent to a certain address. Since it was cheaper to replace the Monk than to repair it, the Monk was cast out in the wilderness to believe whatever it liked. The Monk also owns a somewhat cynical horse, which he was allowed to keep because "horses were so cheap to make". Upon his arrival on Earth, the Monk has several humorous misadventures.
Michael Wenton-Weakes, the spoiled son of wealthy parents, known pejoratively as "Michael Wednesday-Week," which is when he promises to have things done by, such as the next issue of his poorly-managed magazine Fathom. His mother sold Fathom to Gordon Way after his father's accidental death when the latter was changing an electric plug. While Michael seems largely apathetic and yielding to others, the loss of Fathom bothers him much more deeply than anyone realises.
Samuel Taylor Coleridge, writer, one of the founders of the English Romantic Movement. Also a famous laudanum user. In the novel, he is an alumnus of St. Cedd's College. His poems Kubla Khan and Rime of the Ancient Mariner figure prominently in the plot.
Johann Sebastian Bach, the composer, does not in fact exist in the novel's universe. At the beginning of the story Susan, a concert cellist, is having problems practising a piece. During the novel Prof. Chronotis uses his time machine to board the Salaxian ship, still in orbit around the Earth. Inside the ship they encounter elaborate and beautiful music that seems to be the result of the ship's computer system operation, similar to Richard's Anthem program. After they have foiled the ghost's plot and destroyed the ship, Richard finds Susan practising the same music he heard aboard the ship. She tells him it is by Bach. Prof. Chronotis later tells Richard how he managed to retrieve some of the music by introducing it in the Baroque period through the invention of a fake composer.