After you bought your ebook, you are able to download it. After that you can encrypt you .aax with .rtc files from RainbowCrack.

git clone https://github.com/inAudible-NG/tables.git

You can use ffmpeg in order the extract the SHA1 checksum.

$ ffprobe test.aax  # extract SHA1 checksum

Use the scraped Checksum to extract the “activation_bytes”:

$ cd tables && ./rcrack . -h 999a6ab8...

Use the activation_bytes and ffmpeg to convert your ebook:

ffmpeg -activation_bytes 1CEB00DA -i input.aax output.mp3

ffmpeg -i output.mp3 -i cover.jpg -c copy -map 0 -map 1 -metadata:s:v title="Album cover" -metadata:s:v comment="Cover (front)" FINAL-OUTPUT.mp3

DONE!