This study analyzed the English discourse organization of sixty academic book reviews in three disciplines (linguistics, chemistry, economics) published in 1990, to help define book reviews as an academic written genre. Analysis revealed that although book reviews show regularities in information form, function, and content, some variation occurs in terms of how reviewers realize evaluation and description moves across disciplinary boundaries. Results suggest that this variation is produced by the reviewers' tendency to respond to differences in epistemological organization of the three fields (e.g., object of study, methodologies commonly adopted, and the literary tradition) indicating connections between text and context. The study indicates that discursive practices in the disciplines have to be considered in the teaching of English for academic purposes (EAP) to help learners develop more critical and effective reading and writing competencies. Contains 25 references. (Author/MSE)