Strata is a 1981 science fiction comedy novel by Terry Pratchett. It is one of Pratchett's first novels and one of the few purely science fiction novels he wrote, along with The Dark Side of the Sun. Although it takes place in a different fictional universe and is more science fiction than fantasy, it could be said to be a kind of precursor to the Discworld novels, as it also features a flat Earth similar to the Discworld. It has been called a "preconsideration" of Discworld, though the plot and characters are modelled on (or parodies of) the novel Ringworld by Larry Niven. Source: Wikipedia (en)