: To save mobile data, go to Settings in the app and toggle on Download over Wi-Fi only .

: Type a genre (like "mystery") or author into the search bar. Tap the All prices dropdown menu and select Free to filter out paid results.

: To read on other devices, go to your library on play.google.com, click More (three dots) on a book, and select Export . You can typically download them as EPUB or PDF files.

If you are on a computer, you can browse and "purchase" free books via the Google Play Store Website .