M4B is a standard audiobook file type. Presently it is the only file type accepted by BookBaby for sale on the BookBaby Bookshop. Unlike MP3s, M4B files allow for bookmarking one’s spot.
When uploading an audiobook file, you must first zip the M4B file and upload that zipped folder. Click here to learn more about zipping files.
While M4B is primarily an Apple format, PC and Android users can still use the file type, using free and readily available software.
For more information, including links to conversion tools, click here: https://www.lifewire.com/m4b-file-2621958