Ruesch was born in Naples, where his father worked as a textile industrialist and specialist in Pompeian art. He spent the first fourteen years of his life in the city before attending boarding school in Switzerland and enrolling at the University of Zurich to study law. He abandoned his studies in 1932 at the age of nineteen to pursue motor racing, launching a career that would run alongside his growing literary ambitions.
Ruesch entered his first race in 1932, driving an MG at the Klausenrennen hillclimb. Throughout the 1930s he drove a succession of Alfa Romeo and Maserati machinery at smaller events across Europe. His notable machinery included a Maserati 8CM in 1934 and a Maserati 4CS in 1935 and 1936, followed by an Alfa Romeo Grand Prix car in 1936 and 1937. He also participated in a South African racing series in 1937. In the early 1950s he returned to competition briefly, driving a Ferrari 4.1-litre MM sports car. Over the full span of his racing life he started more than one hundred events and won twenty-seven of them.
Ruesch moved to the United States in the late 1930s and began publishing short fiction in popular American magazines. After returning to Naples in 1946, he established himself as a serious novelist. His most widely read works include Top of the World (1950), a novel set in the Arctic that critic Max Eastman in The New York Times Book Review praised as "a brilliant feat of poetic imagination," and The Racer (1953), which drew directly on his years in European motor sport.
Top of the World was adapted into the film The Savage Innocents (1960), directed by Nicholas Ray and starring Anthony Quinn, which received a Golden Palm nomination at the 1960 Cannes Film Festival. The Racer became the basis for the Hollywood film The Racers (1955), starring Kirk Douglas as a reckless Formula One driver. The film was shot on location at Monaco, the Nürburgring, the Mille Miglia route, Circuit de Spa-Francorchamps, and Reims-Gueux.
Following a period living in Rome, Ruesch became a committed opponent of animal testing and devoted the second half of his life to abolishing vivisection. In 1974 he founded the Center for Scientific Information on Vivisection (CIVIS) in Europe. His argument rested on the claim that rodents and other laboratory animals are not physiologically analogous to humans, rendering animal-derived data unreliable and potentially dangerous for medical application. He assembled testimony from medical professionals and researchers in support of this position.
His book Slaughter of the Innocent, published in English by Bantam in 1978 after appearing in European languages under the title Naked Empress, reached a wide audience and was credited with strengthening the animal rights movement in the United States and abroad. A subsequent volume, The Naked Empress, or The Great Medical Fraud, extended the critique to the profit motives of the pharmaceutical industry. Ruesch wrote both works himself in multiple languages, being multilingual, and they are sometimes confused with each other due to overlapping titles.
After World War II, Ruesch settled permanently in Europe, initially returning to Naples and later moving to Lugano, Switzerland, where he died of cancer on 27 August 2007, aged ninety-four. He was survived by his daughter and two sons.
Ruesch occupied an unusual position in twentieth-century motorsport history — a serious competition driver who went on to shape public discourse on biomedical ethics rather than remaining within the racing world. His novel The Racer stands as one of the more authentic literary portrayals of European Grand Prix racing in the pre-war and immediate post-war era, grounded in direct personal experience of the circuits and machines he wrote about.