I have been trying to use the inAudible 191 program, but it only goes to 98% on some books. Can't figure out what I'm doing wrong.
As it was previously mentioned before, the software is not available for downloading and usage on any of the available platforms. However, if you still have the software installed, there might be issues with the conversion because of codecs.
Try installing the following codecs and then start again: http://www.cccp-project.net/
Alternatively, you can use other conversion products instead of this unsupported one: http://software.informer.com/search/audio+converter
Just use another converter to do your converting. It is easy to find a lot. You can try TunesKit, a free AAX to MP3 converter software, Its supportive team is nice. You can ask for any help if you meet troubles.