Shortly before his death, he collaborated with Lapierre on Is New York Burning? (2005), a novel mixing fictional characters and real-life figures that speculates about a terrorist attack on New York City. He also wrote Maze: A Novel (1989), Black Eagles (1995), Le Jour Du Miracle: D-Day Paris (1994) and Tomorrow Belongs To Us (1998).

In 1985, Collins authored Fall From Grace (without Lapierre) about a woman agent sent into occupied France who realizes she may be betrayed by her British masters if necessary.

Paramount Pictures, which was planning a film based on the book, dropped the idea in fear that fanatics would emulate the scenario in real life. The book had such a shocking effect that the French President cancelled the sale of nuclear reactors to Libya, even though it was meant for peaceful purposes. It describes a terrorist attack on New York masterminded by Libya's Colonel Gaddafi. The duo published their first fictional work, The Fifth Horseman, in 1980. It is said they spent $300,000 researching and still emerged wealthy. In 1975, they published Freedom at Midnight, a story of the Indian Independence in 1947, and the subsequent assassination of Mahatma Gandhi in 1948. In 1972, after five years' research and interviews, they published O Jerusalem! about the birth of Israel in 1948, turned into a movie by Elie Chouraqui. In 1967, they co-authored Or I'll Dress you in Mourning about the Spanish bullfighter Manuel Benítez El Cordobés. The book was an instant success and was made into a movie in 1966 by director René Clément, starring Kirk Douglas, Glenn Ford and Alain Delon. In 1965, Collins and Lapierre published their first joint work, Is Paris Burning? (in French Paris brûle-t-il?), a tale of Nazi occupation of the French capital during World War II and Hitler's plans to destroy Paris should it fall into the hands of the Allies. He became the Paris bureau chief in 1961, where he would work until 1964, until he switched to writing books. In 1959, he joined Newsweek as Middle East editor, based in New York. Disillusioned with commerce, he took to journalism and joined the Paris bureau of United Press International in 1956, and became the news editor in Rome in the following year, and later the MidEast bureau chief in Beirut.

He went back to Procter and Gamble and became the products manager of the new foods division in 1955. While serving in the public affairs office of the Allied Headquarters in Paris, from 1953-1955, he met Dominique Lapierre with whom he would write several best-sellers over 43 years. He worked in the advertising department of Procter and Gamble, in Cincinnati, Ohio, before being conscripted into the US Army. Born in West Hartford, Connecticut, he was educated at the Loomis Chaffee Institute in Windsor, Connecticut, and graduated from Yale as a BA in 1951.

Is Paris Burning? by Larry Collins