i downloaded them as a torrent. It was a bit of a hit and miss affair at first as the first two i downloaded were not complete books (a missing chapter or two) I sorted it in the end.. The other way is to actually um.. well...pay for them

Your public library properly has a ton of them (thats metric not imperial

). that would be the way to go.. throw them into your computer, rip them and then stick them onto your MP3 player/Zumo. I'm sure it can be stored in any format you like. Just make sure you don't have it on "random play" The story might be a bit hard to make sense of...
I've used them at this stage for the 35 minute cycle to work with the same idea in mind as you. I found that they are good but also found my mind wandered a bit every now and then.....nice scenery, bike, female of the species..etc goes past and my attention would be taken away for a bit then you miss a bit of the story. And you have a few "what the f*#K are they talking about??....moments. Mind you i had that a bit at school, come to think of it
IN short... not a bad idea...
As i said above go for hunt in the local library, have a play and see what you think.
If you want anything explained in greater detail let me know