The success of the novel freed Knowles to write and to travel. His next two books, the novel Morning in Antibes (1962) and Double Vision: American Thoughts from Abroad (1964), a collection of travel essays, take for their inspiration Knowles' wanderings on the Riviera and in the Middle East.
With Indian Summer (1966), Knowles returned to the theme of boyhood friendships he had explored in A Separate Peace, but critics declared the new novel a disappointment compared to Knowles' first great work. Knowles found a new subject and tone in Spreading Fires (1974), a gothic thriller set on the Riviera. He explored the effects of the past on the present in A Stolen Past (1983) and The Private Life of Axie Reed (1986). His West Virginia childhood inspired A Vein of Riches (1978), a historical novel about coal mining.
Returning to New England themes, Knowles set The Paragon (1971) at Yale University and then finally came back to the fictional Devon School with Peace Breaks Out (1981). Again, critics praised the author's craft, but most agreed that the best novel written by Knowles was his first, A Separate Peace.
