The history of women's spirituality and Christian mysticism demonstrates that women have been influential religious leaders even without benefit of priestly ordination and theological training. St. Catherine of Siena and St. Teresa of Avila are examples of women with visionary gifts of tremendous power. A less well-known Spanish visionary is Sor María of Santo Domingo, a Dominican tertiary of peasant lineage who became so famous for her raptures, austerities, and prophecies that the king, a cardinal, and nobles considered her a living saint.

In 1948 research in the archives of the University of Zaragoza uncovered The Book of Prayer of Sor María of Santo Domingo (originally published around 1518) which had gone unnoticed for centuries. The text includes some of Sor María's ecstatic utterances and representations, and is a first-hand look at a women who in many ways is as representative of the early years of sixteenth century Spain as St. Teresa was of the later years. Giles' book provides the first English translation of this text as well as a study of Sor María and the issues that pushed her into the limelight.