The high cost of textbooks negatively impacts student success. 

In 2016, and again in 2018, Florida State's Virtual Campus conducted a large study of students’ textbook purchasing behaviour.  The results found that students reported various negative effects on their education related to high textbook costs.

The latest findings note "that the cost of textbooks continues to negatively impact student access to required materials and learning. The top 5 highest percentage answers reported by students when asked about the impact of textbook costs are: not purchasing the required textbook (64.2%); taking fewer courses (42.8%); not registering the for a specific course (40.5%); earning a poor grade (35.6%); and dropping a course (22.9%)" (Florida Virtual Campus, 2019).

Attribution:

Graph reused from the 2018 Student and Course Materials Survey by Florida Virtual Campus, licensed under a Creative Commons Attribution 4.0 International License.

The adoption of open textbooks positively impacts student performance.

Students whose faculty chose OER generally performed as well or better than students whose faculty assigned a commercial textbook.

Fischer, Hilton III, Robinson & Wiley, 2015