After graduating from college, Knowles worked as a reporter for the Hartford Courant and occasionally wrote theater reviews for the newspaper. By 1952, he was a freelance writer, with several articles published in Holiday magazine, where he became an associate editor. The success of A Separate Peace gave Knowles the financial freedom to devote himself entirely to writing fiction.
Early in his career, Knowles wrote a novel that was never published and a short story that appeared in a small fiction magazine. He began to experiment with the material that would inspire the early chapters of A Separate Peace with the short story "Phineas," published in Cosmopolitan in 1956.
Knowles submitted his completed novel to American publishers, but the manuscript was rejected. Knowles found a British publisher, Secker and Warburg, for his work. A Separate Peace appeared in 1959 and quickly earned the praise of British reviewers. By the spring of 1960, when the New York edition came out, American critics were acclaiming the novel as well.
