Complex sentence: In 1939 he published his first book, "Gaibéus"; following the author, Gaibéus was not intended as a piece of art, but rather as a report of the way of life of peasants in Ribatejo.
Split into simpler sentences: In 1939 he published his first book, "Gaibéus". According to the author, Gaibéus was not intended as a piece of art, but rather as a report of the way of life of peasants in Ribatejo.