While her work has appeared in many journals and anthologies, The Shadow Keeper marks the appearance of O'Brien's first full-length collection. She explores the major themes of family and personal relationships, the hallmarks of her work. Her style is honest and direct, calling for a similar response in the reader. Her poetry is at once accessible and relevant. In The Shadow Keeper we look at relationships from the perspectives of different generations: a mother's concerns for her daughter, a daughter's rebellion against her parents, and the changing viewpoints of a child grown into adulthood.