The study examines the use of Open Educational Resource (OER) textbooks by 704 students in 9 courses at an American public research university in their learning. It seeks to better understand the effectiveness of OER in comparison to traditional textbooks by surveying how often students read OER textbooks and examining how instructors in the courses are teaching using OER. The study found an alarming trend, the impact of OER has been limited because of students not reading assigned textbooks, and instructors not actively teaching with them. This may be reflective of a phenomenon not previously noticed by OER researchers, high textbook prices causing many instructors to abandon serious use of textbooks while students are still painfully purchasing them, causing students to develop a habit of not reading textbooks. Findings of the study suggests that student textbook use, their attitudes towards textbooks and how instructors are teaching with OER textbooks are important factors in assessing the effectiveness of OER.