A Dominant Church traces the story of the diocese of Achonry through the nineteenth and first half of the twentieth centuries, highlighting local participation in the great national movements from the Tithe War and the Great Famine, to World War I, the Black 'n' Tan War and the Civil War.
Despite its remoteness the diocese played a surprisingly central role in some national events. Edward Duffy from Ballaghadereen was one of the leading Fenians and succeeded James Stephens as the head of that movement. The diocese was the very cockpit of the Land War, producing such notables as Michael Davitt, John Dillon, Fr Denis O'Hara and Anne Deane, President of the Ladies' Land League.

'The Devotional Revolution', the transformation of Irish spirituality from the homespun and home-based spirituality to that of the town-centred spirituality imported from continental Europe promoted by the religious orders in parish missions, also features in the book.