Mary Marston is a novel by George MacDonald, written in 1881 and later republished under the title A Daughter's Devotion.Written at the height of George MacDonald's literary career, the story centers around the life of a simple merchant's daughter. Mary Marston's unswerving commitment to love God and others is contrasted with a backdrop of an array of characters and a complex and sometimes mysterious plot.It is a story of a woman who loves a man, and teaches him to change.