For the past decade or so, I have created primary document readers for my class using copyright-permitted documents or documents where the author has granted permission for educational purposes. These would usually be about 200-300 pages. I would send them to the copy center for binding and then these would be sold in the bookstore to the students. The cost to the student was about $15-20.
There were three issues that were of concern. First, these books were not too expensive, but I was exploring ways to move the sourcebooks online so the students did not have this cost. Also, there were always problems determining how many sourcebooks to order since some students would share. Unsold books were charged to my department. Second, I wanted the students to be able to have the documents in class during discussion. This would necessitate having the documents in a format where they would be available on multiple devices - phones, laptops, tablets, iPads, Nooks, etc. Third, I did not want to simply link to the documents due to the fact that online links sometimes disappear. I also wanted the students to be able to work offline in case they did not have access to the Internet.
Corning, Caitlin, "Creating ePub eBooks to Enhance Student Learning" (2015). Digital Teaching and Learning -- Case Studies. Paper 1.