= Command line utility: abbinder 
As of 1.18 it's part of main bundler. Path to the utility is:
    AudioBookBinder.app/Contents/MacOS/abbinder

== Usage
abbinder [-hsv] [-c 1|2] [-r samplerate] [-a author] [-t title] 
  [-i filelist] outfile [@chapter_1@ infile @chapter_2@ ...]
        -a author       set book author
        -c 1|2          number of channels in audiobook. Default: 2
        -C file.png     cover image
        -e              alias for -E ''
        -E template     make each file a chapter with name defined by template
                            %N - chapter number
                            %a - artis (obtained from source file)
                            %t - title (obtained from source file)
        -h              show this message
        -i file         get input files list from file, "-" for standard input
        -q              quiet mode (no output)
        -r rate         sample rate of audiobook. Default: 44100
        -s              skip errors and go on with conversion
        -t title        set book title
        -v              print some info on files being converted

Attributes for -a and -t arguments (author and title) should be in UTF8.
Only jpeg and png are supported as cover page format. 
Valid sample rate values:
    8000, 11025, 12000, 16000, 22050, 24000, 32000, 44100, 48000

Chapters could be set either by chapter markers in file list or by
treating each source file as a chapter.  In former case chapter name is
provided by user and should be enclosed in '@' characters to distinguish
it from file names. e.g.:
    abbinder book.m4b '@Chapter 1@' track01.mp3 '@Chapter 2@' track02.mp3

Chapter names in the latter case are generated for each input file and 
may contain some escaped sequences that would be expanded when creating 
a chapter. Template is provided as argument for -E switch. 
Available sequences:
    %N - number of chapter, starts from 1
    %a - value of 'artist' tag from source file
    %t - value of 'title' tag from source file

So previous example could be rewritten like:
    abbinder -E 'Chapter %N' track01.mp3 track02.mp3

== Examples

Convert one file to m4b
  bash$ abbinder book.m4b myfile.mp3

Convert several files to mono m4b with sample rate 8000
  bash$ abbinder -r 8000 -c 1 book.m4b myfile.mp3 myfile2.mp3

Convert all mp3 files in directory and set author, title and cover image
  bash$ find ./dir -name '*mp3' > list
  bash$ abbinder -i list -a Author -t Title -C ~/cover.png out.m4b

Convert three-chapter book with explicit chapter names:
  bash$ abbinder book.m4b '@The very beginning@' 01.mp3 \
      '@In the middle of something@' 02.mp3 \
      '@Ashes to ashes and dust to dust@' 03.mp3

Convert several short-stories files and make each of them a chapter
  bash$ abbinder -E '%t' story01.mp3 story02.mp3 story03.mp3