The audio isn't quite finished, but it's very close, and certainly listenable. I hope you take the time to check it out, and if you like what you hear please consider purchasing the ebook version (only 99 cents!) from Amazon.com or Barnes and Noble.com.
The audiobook version will be forthcoming on CD, either in MP3 format or (space permitting) standard CD audio. Pricing information will be made available once it is finished (I'm not quite sure myself how much the production costs will be, but the price will be under $10).