Bellow's fourth novel, Seize the Day was published as a novella in 1956 in a volume that also included three short stories—"A Father-to-Be," "Looking for Mr. Green," and "The Gonzaga Manuscripts"—and a play, The Wrecker. Considered by many critics to be Bellow's finest work of fiction, the novella was immediately singled out from among its companion pieces as a major work. The powerful impact of Seize the Day comes from its tightly constructed plot; from Bellow's ability to control effectively in a concentrated form such enormous themes as victimization, alienation, and human connection; and from his creation of Tommy Wilhelm, one of his most moving protagonists.
Bellow's work before Seize the Day had attracted the attention of readers and critics, but he was particularly praised for his achievement in this fourth novel, which Baker says "demonstrates his attainment of full artistic maturity." Seize the Day deals with themes familiar to readers of Bellow's fiction, such as that of the father-son relationship, yet in this novella the concentrated structure enabled Bellow to render this theme more intensely.
At the heart of the action in Seize the Day, Tommy Wilhelm's relationship with his father revolves around Tommy's neediness and his father's disapproval of him. Tommy's problems with his father feed yet another theme of the novel and of Bellow's fiction in general: alienation from oneself and from humanity. Tommy feels cut off not only from his father and from the rest of his family—his sister, his dead mother, his estranged wife and their two sons—but he also feels alienated from himself and from everyone he meets. Bellow's ability to treat weighty themes in Seize the Day, while making Tommy Wilhelm a pitiable yet sympathetic character, explains the success of this novella: it is capable of seizing both the reader's mind and heart.