An English fiction writer, poet, and literary reviewer, she is most remembered for her Balkan and Levant novel trilogies, which are known, collectively, as the Fortunes of War series. Common themes of her work include colonialism, war, alienation, and feminism.
She wrote three detective novels: Rose of Rubies, Here is Murder, and The Black Scarab. All of these works, written under the pen name of Jacob Morrow, were serialized in the Portsmouth News in 1929.
She wrote reviews for The Spectator, The Sunday Times, The Observer, Punch, and several other publications.
She met her husband, BBC radio producer R.D. "Reggie" Smith, in 1939. Despite infidelities on both sides, the marriage lasted until Manning's death.
The BBC TV adaptation of her Fortunes of War series starred Kenneth Branagh and Emma Thompson.