Ensuring that an OER textbook provides exceptional learning experiences and accessibility requires rigorous stages of writing, expert peer reviews, and user testing. In this OER research project, the objectives were to provide a scholarly textbook for a Master in Library and Information Science (MLIS) degree program that reflected current technologies and concepts in information retrieval, supported the course learning objectives, and was aligned with the scaffolded hands-on assignments. A key priority in the research design was for the book to undergo both expert peer reviews and extensive user testing with students. To support students in the different modes in which they learn, the book was developed with multimedia content, including embedded videos, recordings, and supplemental readings. All materials were thoroughly tested to meet current accessibility standards. The study combined qualitative and quantitative methodologies in four phases of progressive research: (1) alpha test with semi-structured interviews and follow-up questionnaires (n = 4); (2) domain expert peer reviews (n = 10); (3) beta test pilot course with questionnaires (n = 58); and (4) course delivery (n = 630) with survey (n = 102). The project can serve as a model for other courses in higher education, particularly online courses with high enrollment figures. In addition, elements from the study findings can help to guide any project involving the development of high-quality OER textbooks. Three elements were found to be critical to the success of the OER textbook: iterative stages of user testing with students, peer reviews with subject matter experts (SMEs) to evaluate all subtopics, and accessibility testing to ensure inclusivity.