In 1926, Sereni joined the Italian Communist Party and one year later he graduated in agronomy in Portici, starting shortly after a work of proselytism in the Neapolitan area, where he met Giorgio Amendola.

Amnestied in 1935, Sereni fled to Paris with his wife Xenia Silberberg, known by the name of Marina, and their daughter Lea; there, he was responsible for cultural work and served as editor-in-chief of the magazines Stato Operaio and La voce degli italiani.

A polyglot, Sereni knew German, English, French, Russian, Greek, Latin, Hebrew, Japanese, and several dead cuneiform languages such as Akkadian, Sumerian and Hittite.

Among his theoretical and historical works are Il capitalismo nelle campagne ("Capitalism in the Countryside"), Il Mezzogiorno all'opposizione ("Mezzogiorno in the Opposition"), La questione agraria nella rinascita nazionale italiana ("The Agrarian Question in the Italian National Rebirth") and La rivoluzione italiana ("The Italian Revolution"); altogether, his bibliography contains 1071 writings, the first dating back to 1930.

His daughter narrated Sereni's political and family history in the historical novel Il gioco dei regni ("The Play of Kingdoms"), published by Giunti in 1993.