APA
Note that APA style requires you to add the type of e-device, where you retrieved the eBook, and the URL or doi.
Example:
De Huff, E. W. (n.d.). Taytay’s tales: Traditional Pueblo Indian tales. Retrieved from
http://digital.library.upenn.edu/women/dehuff/taytay/taytay.html
Stoker, B. (1897). Dracula [Kindle DX version]. Retrieved from Amazon.com
These examples come from Purdue OWL: APA Formatting and Style Guide
What is OverDrive?