Career
They lived in Björknäs at Hållsviken west of Trosa in Södermanland. The father was—in addition to his work— a fiddler. Their son Gustav had since childhood, both heard and played on the fiddle—a musical instrument which he handled with skill throughout life.
He was fascinated by folklore, mystery and dreams.
After school Sandgren became a laborer and worked for five years at Cloetta chocolate in Ljungsbro. He eventually became a full-time writer, and was to have 47 books behind him when he died in 1983.
Together with Harry Martinson, Artur Lundkvist, Erik Asklund and Josef Kjellgren he formed the literary group Fem unga (Five young ones). Sometimes he wrote under the pseudonym Gabriel Linde.
The last name Linde referred to the croft where he stayed in the summer of 1933, located about a kilometre southeast of Norrvrå station in Hölö in Södermanland.