The title refers to Italy's two-decade period of postwar economic expansion, as rapid modernization and industrialization created a huge new middle class and a generation of upwardly mobile movers and shakers. Giovanni Alberti (Alberto Sordi) is an amiable middle manager up to his eyeballs in debt. He buys fancy coats and cars to impress his wife, Silvia (Gianna Maria Canale), the daughter of a pious police chief, and spends his time trying to keep up with his fun-loving nouveau riche friends.
Giovanni's ship appears to have finally come in when he approaches one-eyed industrialist Bausetti (Ettore Geri) with a get-rich-quick construction scheme and immediately attracts the attention of the man's wife (Mariolina Bovo). Giovanni thinks Mrs. Bausetti wants his body; turns out she wants his eye -- as in his literal cornea.
De Sica and Zavattini nail how money and power infect almost every human interaction; they paint a portrait of a culture in which everything is transactional. The frame is crowded with brand names, via billboards and bus advertisements and neon signs. (Cinzano! Philips! Kit Kat!) In the background, we often see the giant apartment complexes that sprouted up during the boom years. For all that, however, Il Boom makes no attempt to seduce us. We see the spiritual corruption from the first frame.