He published his first mystery, Il banchiere assassinato, in 1935. He subsequently wrote some twenty crime books, whose protagonist is Commissario Carlo De Vincenzi of the squadra mobile of Milan. Some of them were adapted for television by Radiotelevisione Italiana in 1974–1977, with Paolo Stoppa playing the role of De Vincenzi.
Despite the success of the books, the Fascist government banned them.
De Angelis was arrested in 1943, accused of being Anti-Fascist. After a few months he was freed but soon afterwards he was beaten up by a Fascist activist, and died at Bellagio of the wounds he had received.