Format:
Author, A. A. (Year). Title of book [E-reader version, if applicable]. (pp. xxx-xxx) Retrieved from http://xxxx
Example:
Smith, J. J. (2014). Nature of citation. [Kindle Fire]. (pp. 205-232) Retrieved from http://www.amazon.com
If there are no page numbers:
Some Kindles do not have page numbers. According to the APA Style blog
Format:
Author, A. A. (Year). Title of book [E-reader version, if applicable]. Retrieved from http://xxxx
Example:
Smith, J. J. (2014). Nature of citation. [Kindle Fire]. Retrieved from http://www.amazon.com