To transfer purchased books from the Google Play Store to your pc/laptop/tablet/nook/kindle/etc follow the below steps:
1. On your computer, go to Google books (http://books.google.com/) and then click on where it says “My Library”
2. Choose the book you want to download, and then click go to the sprocket in the upper right hand corner. This page lists an overview of the book, along with other information about the title.
3. Click on either the EPUB or PDF link for the Google eBook file that you would like to transfer. This will download the appropriate file onto your computer.
4. Now transfer to your device and enjoy!