Original script by shrsv was updated with GUI inteface and export for Open Mind Map format.
Now you can just run python script and select a book you want to export.
Simplest way to get your highlights:
$ poetry install
$ poetry run python3 ibooks_highlights_exporter.py
You can help with building a bundle for Mac OS with py2app. There were some problems with following official tutorials, related to importing jinja2 module.
Building a package is as simple as:
$ python setup.py py2app
But then application refuses to run from system (though it succesfully runs from terminal).
You can reference these links to begin with: