We are wanting to do the same thing; e-books for rent. I don't know how to purchase the ebooks, or how to process it on our website. Have you learned more?
I have thought about offering this feature to bring our library into the future. If you receive info, please pass it on to me.
I am working on acquiring Overdrive for my church library, and just posted my report on my blog at: http://www.colleengreene.com/2014/01/14/investigating-overdrive-ebo...
Systems Librarian, Pollak Library, California State University, Fullerton
President, Evangelical Church Library Association, Southern California chapter
Member, Rose Drive Friends Church, Church Library Committee
If you have a newsletter, perhaps you could let your patrons know about the free ebooks they can download to their own ereaders. www.christianbook.com has a list of 30 to 40 free books. You can then go to the ebook site of your choice and download them. Several publishers offer newsletters which they send periodically of available free ebooks such as :
Most title are only available free for a limited period.
I have been able to get several hundred free Christian ebooks over the last several years this way.