Android’s physical navigation buttons are back on Googlebooks, but not the way you think
A common misconception I've seen with Googlebooks is that the Quick Insert and Google logo keys are new. They're not, as they first debuted a couple of years ago on some Chromebooks.
Reported so far by one publisher.
Summary from The Verge.
Reporting1
The Verge Android’s physical navigation buttons are back on Googlebooks, but not the way you think · Antonio G. Di Benedetto