Houselander was a prolific writer and contributed many pieces to religious magazines, such as the "Messenger of the Sacred Heart" and "The Children's Messenger". Her first book, "This War is the Passion", was published in 1941 and in it she placed the suffering of the individual and its meaning within the mystical Body of Christ. For a time, she became publisher Sheed & Ward's best selling writer, drawing praise from people such as Ronald Knox:"she seemed to see everything for the first time, and the driest of doctrinal considerations shone out like a restored picture when she had finished with it. And her writing was always natural; she seemed to find no difficulty in getting the right word; no, not merely the right word, the telling word, that left you gasping."