Mannuzzu's most successful novel is Procedura (1988. Einaudi), winner of Italy's Viareggio Prize in 1989. It is a detective story where the nameless narrator is an investigative judge who has to discover Valerio Garau's killer. Garau is an attorney from Sassari in Sardinia, who is poisoned to death while having coffee with his lover. The story unfolds over two years, 1978 and 1979, during a critical period for Italy, marked by a wave of terrorism. In 2000 the director Antonello Grimaldi made the film Un delitto impossibile from this novel, which is also considered (with the coeval L'oro di Fraus by Giulio Angioni), the origin of a genre of Sardinian detective stories (giallo sardo).[5][6]