Born in Council Bluffs, Iowa, Beer graduated from Yale University in 1911 and studied law at Columbia University from 1911 through 1913.

Beer was best known for his biographies of Stephen Crane (1923) and Mark Hanna (1929), as well as his study of American manners during the 1890s, The Mauve Decade (1926). He published three novels—The Fair Rewards (1922), Sandoval: A Romance of Bad Manners (1924), and The Road to Heaven: A Romance of Morals (1928)—in addition to more than 130 short stories in The Saturday Evening Post. In 1927, with the help of Eugene Spreicher and Atherton Curtis, Beer produced George W. Bellows: His Lithographs, a catalogue raisonné, with reproductions of the artist's black-and-white lithographs.

A collection of Beer's short stories was published under the title Mrs. Egg and Other Barbarians in 1933. After Beer's death of a heart attack in his apartment in the Hotel Albert in New York, another collection of his short stories, edited by Wilson Follett, was published as Mrs. Egg and Other Americans: Collected Stories (1947). These two collections are frequently confused: for example, the Columbia Encyclopedia entry on Beer gives the 1933 title for Follet's 1947 collection.

During the 1920s and 1930s, Beer was widely celebrated and much read. His fiction may have influenced such modernists as William Faulkner and F. Scott Fitzgerald. According to archivist Robert Nedelkoff,