This paper presents a model and conceptual framework for textbook research. The model will help scholars from a variety of disciplines approach textbook research from a common theoretical grounding and later compare and synthesize their findings using agreed-upon categories and a shared vocabulary. The author first describes two rudimentary models for textbook research developed by Cronbach in 1955 and by Tudor in 1978. She then presents her own systems approach to textbook study. The model is based on an ecological paradigm. It positions the textbook within the educational suprasystem of the socio-cultural metasystem. The textbook is viewed in relation to five subsystems of the educational system: the educational delivery system, the family system, the government system, the knowledge production system, and the knowledge distribution system. The textbook shares in the history of ideas, the history of education, the technology of printing, research and theory on the teaching-learning process, the sociology of knowledge, and the commerce of publishing. In use, the textbook enters the classroom subsystem of the educational delivery system. There texts generate or fail to generate processes that shape minds, attitudes, and ideas. Textbooks-in-use produce both intended and unintended outcomes. From the perspective of the systems model, such feedback may be viewed as a function of ecological fit. (RM)