Loose MP3s, one book in Apple Books.

It binds the library you already have.

Point it at one book folder, or a parent folder of many books. Nested wrappers (Calibre-style 43/Title trees) become a folder list on the left. Already-made .m4b files show as already bound so you do not encode them twice.

Metadata is filled from MP3 tags, then OPF/EPUB, then the ebook filename, then the folder name. You can rewrite title, author, narrator, cover, and every chapter before you build. Uncheck a credits track. Play a chapter to be sure. Save the file next to the book, or into ~/Music/Audiobooks.

The finished file is marked as an audiobook for Apple Books (stik=2) with a chapter track. Drop it on Books, or use Open in Books at the bottom of the window.

How to bind a book

1. 1

   Open a folder

   Choose a single book of numbered MP3s, or a library folder. Nested wrappers are scanned automatically. Nothing is scanned until you open a folder. The status bar names the folder being read.

2. 2

   Pick a level, if you need to

   When books sit under extra folders, use the folder tree on the left. Filter by title, author, or narrator. Already-bound files stay unchecked.

3. 3

   Edit, skip, listen

   Fix title and author. Change the cover. Uncheck chapters you do not want. Play any chapter from the list. Bitrate and save location sit under Open Folder. After a build, compare original audio with the .m4b chapter by chapter.

4. 4

   Build

   Save in the book folder, or to Music/Audiobooks. Then Show in Finder, Open in Books, or Verify at the bottom of the window. If chapter counts and durations match, you can move the original audio files to Trash.