The guided use of selected books as an adjunct to treatment is applicable to patients in all stages of life and with a variety of problems. This paper describes the authors' experience using books as an adjunct to therapy with psychiatric patients. The authors define the term, review the literature, and set out the objectives of bibliotherapy. The paper presents some principles to follow when assigning books, and examples of books used for common problems. Finally, examples are given of bibliotherapy in action at two Ontario hospitals, and some future directions are suggested.