The high cost of textbooks is of concern not only to college students but also to society as a whole. Open textbooks promise the same educational benefits as traditional textbooks; however, their efficacy remains largely untested. We report on a case study about one community college's adoption of a free online psychology textbook. During the fall semester 2011, 690 students used this book. Compared with students using a traditional text in the spring of 2011, students who used the free online textbook scored higher on departmental final examinations, had higher grade point averages in the class and had higher retention rates. (Contains 3 tables and 1 note.)