Writer-film producer Shapiro’s engagingly breezy first novel describes, in parallel first-person narratives, the cultural collision of a sort of Out-of-Australia, feisty American woman and the Aussie rock musician who sends her away to save her life. Anyway, that’s his story. She is Rachel Ganelli, who leaves the rock band (Tall Poppies) she’s been rooming with Down Under, and returns to America, when an ex-band member is gunned down by the Mafia and everybody realizes that Rachel is a material witness. He is Colin, the group’s bassist, whose sexual allure is somewhat dimmed for Rachel when she eventually learns that he hatched the “demented Peggy Lee-inspired plot” meant to revive the Tall Poppies’ flagging celebrity. Meantime, the supposed dead man, Stuart, has shown up in America, and Rachel must enlist her reluctant brother and an old high school friend to help Stuart kick his heroin habit. Then Rachel’s parents unexpectedly return from their vacation, Rachel gets jury duty and is sequestered to consider the fate of an unlikely suburban murderess (“We’re not buying the saintly grandmother act. She’ll get life”). These and other agreeably ludicrous misadventures are brought to a more or less satisfying conclusion (did I mention that Tall Poppies gets a gig in New York City ?) in a disarmingly loose novel that wanders amicably all through Rachel’s and Colin’s histories, fantasies, and respective fixations on each one’s indigenous music, film, and TV culture. Shapiro’s high-concept premise pays off in a truckload of enjoyable gags (the title denotes a favorite practical joke), hilarious characterizations (the good-natured, essentially moribund Stuart is particularly entertaining), and irresistible non sequiturs (“Hannah started converting her cats to vegetarianism”). And it should surprise nobody when the story climaxes with a coincidence straight out of the 18th-century novel. The Unexpected Salami is a hell of a mess, but has commendable energy and marches along smartly to its own arrhythmic, offbeat beat.