Zooming in macOS iBooks
It's not natively supported in the iBook app to zoom or change text size of .ibooks files

However I found a way to zoom in. It's maybe not the most elegant solution. But it can be very useful. I also suggest you play with the Zoom settings to get the mode that's best for you.


Choose Apple menu > System Preferences, click Accessibility, and then click Zoom.
Select “Use keyboard shortcuts to zoom.”

To zoom in use alt + cmd + =
To zoom out use alt + cmd + -