After teaching for eighteen years at the Synge Street CBS in Dublin, MacManus joined the staff of Radio Éireann (precursor to RTÉ, the Irish national broadcasting entity) in 1948 as Director of Features.
[1] MacManus began writing while still teaching and first published a trilogy set in Penal times and concerning the life of Donnchadh Ruadh Mac Conmara, an author of Irish poetry in the Irish-language.
The location was the fictional "Dombridge", based on Kilkenny, and deal with established themes of Irish rural life: obsessions with land, sexual frustration, and the trials of emigration and return.
[2] In his last two novels, MacManus descended into the depths of theological debate: The Fire in the Dust (1950) was followed by American Son (1959), a remarkable dialogue between conflicting modes of belief which reveals the strong influence of Roman Catholicism on the author.
Among the names who have featured and who have gone on to win acclaim in Ireland and internationally are Cónal Creedon, Claire Keegan, Molly McCloskey, Anthony Glavin, Mary O'Donnell and Ivy Bannister.