Pétur received his Master's degree in Philosophy from the Université d'Aix-Marseille in 1975. His first work, the poetry book Splunkunýr dagur (A Brand New Day) was published in 1973, but before then Pétur's poems had been published in Tímarit Máls og menningar. The novel Punktur punktur komma strik appeared in 1976 to acclaim, the first of four books about the boy Andri. A film by Þorsteinn Jónsson, based on the book, also became highly popular in Iceland. The last book about Andri, Sagan öll (The Whole Story), was nominated for the Nordic Concil's Literature Prize in 1987. Pétur has brought out a number of other novels, two of which have been nominated for the Icelandic Literary Prize.