How to report bugs to Google? (re Google Play Books)

OK so I read books on my Nexus 7 and there is an option in the Google Play Books app to turn pages with the volume rocker (necessary for one handed page turning while palming the device). As far as I can tell there is a bug that prevents it from working unless the menu is visible (which obviously makes it impossible to use as intended). This hasn't been fixed for many months now, reviews on the app store don't seem to penetrate their bubble, and Google searches about reporting bugs in core Google apps come up empty. How would I go about making them aware of this bug? You would think the people developing it would catch a bug like that considering there are only a few options so I'm going to be charitable and suppose it's a device specific bug.