His parents were Bert Japin, a teacher and writer of detective novels, and Annie Japin-van Arnhem. After a difficult childhood - his father killed himself when he was twelve years old - Japin entered the Kleinkunstacademie in Amsterdam, where he trained as an actor. He was also briefly an opera singer at De Nederlandse Opera in Amsterdam.
His first novel, De zwarte met het witte hart (1997), translated as The Two Hearts of Kwasi Boachi, was the story of two Ashanti princes, Kwame Poku and Kwasi Boachi, who were taken from today's Ghana and given as gifts to the Dutch king Willem II in 1837. Based in part on Japin's own traumatic youth, and based on ten years of research in the Netherlands, Germany, Africa, and Indonesia, the book became a bestseller and is considered to be a classic of modern Dutch literature. In November 2007, an opera based on the novel premiered in Rotterdam, with an English libretto by Arthur Japin and music by the British composer Jonathan Dove.
His second book, De droom van de leeuw, (2002), is a novelized version of his relationship with the Dutch actress and novelist Rosita Steenbeek in Rome, where Steenbeek became the last lover of the Italian director Federico Fellini.
His third novel, Een schitterend gebrek, translated as In Lucia's Eyes (2003), was a return to the historical novel, about Casanova's first lover, Lucia, who, he reports in his Memoirs, inexplicably abandoned him in his youth, only to resurface years later as a hideous prostitute in an Amsterdam brothel.
His forthcoming novel, De overgave, to be translated as Someone Found, takes the subject of the 19th-century Texas Indian wars, dramatizing the story of the Fort Parker Massacre of 1836, in which a white girl, Cynthia Ann Parker, was taken as a Comanche hostage, later becoming the mother of the famous Comanche chief Quanah Parker.
Japin has also published several volumes of stories. The first two, Magonische verhalen and De vierde wand, were gathered into the omnibus Alle verhalen, (2005). Magonische verhalen was made into the film Magonia by the Dutch director Ineke Smits. Japin was the author of the Boekenweekgeschenk (Book Week Gift) 2006, De grote wereld, a short novel about a pair of circus-performing dwarves caught in Nazi Germany, which had a record first printing of 813,000 copies. He has won almost every prestigious prize in Dutch literature, including the Libris Prize for In Lucia's Eyes.