An article about this work has been published:
Hendricks, C., Reinsberg, S. A., & Rieger, G. W. (2017). The Adoption of an Open Textbook in a Large Physics Course: An Analysis of Cost, Outcomes, Use, and Perceptions. The International Review of Research in Open and Distributed Learning, 18(4). http://www.irrodl.org/index.php/irrodl/article/view/3006