To create read aloud content for Apple Books, you need:
a fixed-layout book
a narrative audio file
an audio editing tool for marking times within an audio file
Note: This document has instructions for marking start times and end times in an audio file using Audacity, a free, cross-platform audio editing tool. You can use another audio editing tool to mark start and end times in an audio file. Steps for marking start and end times in an audio file will vary depending on the tool you are using.