Have you heard of Booktrack? They contacted me recently to let me know about their service and invited me to try it out for myself. So I decided to check them out. Here's what their site says ...

Booktrack is transforming reading the way sound transformed silent film 
Booktrack offers a new content creation and distribution platform that turns reading into an immersive movie-like experience. Booktrack’s patented technology lets anyone add a synchronized movie-style soundtrack to an e-book...