When you upload an e-book on Amazon Kindle, it is audible enabled to a single computer-generated voice. You can convert your MS Word or Pdf file to an audio book for a wide range of prices.
Here is what some of the voices sound like: http://www.naturalreaders.com/sample.php
Scroll to the bottom of the page on this link: the Developer Version offers eight voices. Exactly how you can weave them into a book recording, I don't know, but they do have support staff you can ask. http://www.naturalreaders.com/order_information.php#voices
Have a listen. I'll let you be the judge. If anyone has been able to use such software to record a talking book, post a comment and let me know how it went. I have contacted recording studio engineers to ask if you can enhance computer-generated voices to make them more like real narrators. The answer was "no" across the board. Who knows? Technology is constantly changing.