I put together a free tool to automate the .aa to mp3 / wav process. I call it inAudible and you can find it
here.
Besides installing the Audible Manager (which all Audible users should have, anyway) it shouldn't require any additional codecs or libraries.
Features:
- Includes and installs required codecs and DLLs
- Includes LAME and will auto-encode if desired
- Allows for multiple input files and a single file destination mask
- Will split the encoded file into smaller, more managable files using silence detection to find chapter breaks
I have tested it on XP, Win7 x64 and Win 8.1. Seems to work, although 8.1 needed a reboot.