She wrote biographies of John Bunyan, Trappist monk Thomas Merton, Thérèse of Lisieux,[2] and Alan Watts,[3] as well as books covering such diverse topics as the spiritual life of aboriginals, medieval women mystics, and the Church of England.
She also wrote a popular series of children's novels set in medieval England and Scotland: Wise Child, its prequel spinoff Juniper, and its immediate sequel Colman.
[2] Furlong began her writing career in 1956 as a feature writer for Truth magazine, where she met Bernard Levin, who became a lifelong friend.
She then joined The Spectator as its religious correspondent from 1958 until 1960, before moving to the Daily Mail, where she remained for the next eight years.
[3] While in her 30s Furlong had used LSD, an experience she described in her book Travelling In (1971); the work was banned from Church of Scotland bookshops.