Add podcast-like chapters to audiobooks
You can do it with Garageband on a Mac, or using a separate utility on Windows.

Mac with Garageband

There's a detailed guide here, but the concise version is:


Create a new Podcast in Garageband.
Delete the placeholder tracks (the Podcast track can't be deleted), then drag in the audio file you want to add chapters to.
Select the Podcast track, make sure the editor is open (&#x2318;E).
Move the playhead to the position you want a chapter at, and click Add Marker. Repeat for each chapter position you want. You can add titles if desired.
Export to disk or iTunes via the Share menu.


If you want the files to appear as audiobooks in iTunes, you may need to select them (in iTunes), and change the Media Kind (Get Info/&#x2318;I, Options tab) to Audiobook.

Windows using Chapter and Verse


Download the free Chapter and Verse program. There are probably others out there, but this one seems to do the trick fairly simply and is free.
Click Add Files to import your audio track. If it's not in AAC format, it will prompt you to convert it.
Go to the Chapters tab and add your chapters as necessary.
Click the Build button to save the file, then import it to iTunes as desired.