I wanted Brian Green's audio book, "The Fabric of the Cosmos: Space, Time, and the Texture of Reality" but the price stopped me. Now I have it through a free trial offer. Went cross country skiing while being read to, nice.
The free offer is available through: http://www.audible.com/
Search out the above author and one button should say "Learn how to get this FREE"
I am no longer a member of audible.com as their selection of physics related e-books was limited and very expensive, see Feynman Lectures in Physics as an example of price.
Moderators, please move this if not appropriate here, my apologies in advance. Was not allowed to post to "Math & Science Learning Materials".