After studying English at Trinity College Dublin, where she also took a diploma in education, she soon married. She initially planned a career in teaching but instead opened a creche for children of working mothers while bringing up her son Alexander.
Her first book, Gift Horse, published in 1979, also won an award and she followed this in the early 1980s by branching out into newspaper work with a column in the Irish Independent.
A second career opened in book publishing when several years later she joined Poolbeg, one of a clutch of small but prolific Irish literary houses. Working alongside the enthusiastic publisher Phil MacDermott, she became editorial director and won wide respect through her discerning eye for emerging new writers.
MacDermott was full of praise for the contribution of his new lieutenant, whose contribution effectively resurrected a company that by his own admission had wandered after its major 1983 success with The Boss, Joe Joyce and Peter Murtagh's classic warts-and-all biography of Charles Haughey. Joyce observed with admiration how O'Brien "was able to come up with a clutch of blockbusters as if from nowhere". Several were sold on for wider paperback distribution through British and international publishers.
Among her finds was Marian Keyes, best-selling author of Water Melons and Lucy Sullivan is Getting Married. She praised O'Brien's unwillingness to allow her any "soft options" in her story-telling. Charting in one work the painful experience of recovery from addiction, Keyes recalled in the Irish Times, "I begged to be absolved from it, but Kate was quite matter of fact. `You've got to write the book that wants to be written,' she kept saying."
MacDermott described O'Brien as "irreplaceable, a unique and wonderful talent". She was the daughter of the formidable and controversial diplomat, journalist and author Conor Cruise O'Brien, one-time editor-in-chief of the Observer and recently adviser to the small UK Unionist Party in Northern Ireland. Her mother is the Derry-born Christine Foster.
Kate Cruise O'Brien, writer and publisher: born Dublin 1948; married 1971 Joseph Kearney (one son); died Dublin 26 March 1998.