He began his literary career at an early age, always prolific and indefatigable: lectures, speeches, historical and patriotic articles, poems, narrative prose culminating in *Genti e cose della montagna*, *Novelle e paesi valdostani* (his most genuine and flavourful work), *I Castelli Valdostani* and *Impressioni d'America*, some thirty plays, one-act pieces and opera libretti, among which the most important are *Tristi amori*, *I diritti dell'anima* and *Come le foglie* (see the whole *Teatro*, edited by P. Nardi, 2 vols., Milan 1948). With his easy yet subtle psychology, G. depicted the minor sentimental crises of late-19th-century bourgeois society, whose problems and passions he understood and exploited.
Bibl.: E. Marangoni, *Il capolavoro di G. G.*, Milan 1906; H. Bordeaux, *La vie au théâtre*, Paris 1909, passim; B. Croce, *La lett. della nuova Italia*, II, Bari 1914, pp. 213-30; L. Garajo Armò, *Il teatro di G. G.*, Palermo 1925; M. Rumor, *G. G.*, Padua 1940; G. Petroccchi, *Scrittori piemontesi del secondo Ottocento*, Turin 1948, pp. 37-49; D. Donelli, *G. G.*, Milan 1948; P. Nardi, *G. G.*, ibid. 1949.