Before downloading an eBook you will need to install an ereader application such as Google Play Books.
Once installed you can download the EPUB file directly to your device. If Google Play Books doesn’t open the eBook automatically, please follow the ‘Upload PDF & EPUB files’ instructions on Google Play Help.
Note that MOBI files are not compatible with Google Play Books. If you want to read a MOBI eBook on an Android device you will need to install the Kindle app following the downloading and reading on Kindle devices and apps link.