There is a pretty easy way to unlock your Audible books. Once downloaded, you can use ffmpeg and specified rcrack rainbow tables to do that.

There are three easy steps:

  • Detect the file hash
  • Retrieve the encryption key for the hash
  • Unlock the file and convert the audio format

There is instruction in the of the GitHub repository.

But the reason why posting this, is that I created a script to convert many .aax files unattended as a command line bash script. In addition, it removes the Audible intro and outro voice over from every track. To use it, you just need to clone the repository by following the link below and to install the required software as described in the there. It should work on Windows and Linux (untested).

Repository on GitHub