Click on the download button above on your phone or tablet or the link I texted you. That will open up a Google Drive window in your web browser. Google Drive doesn't understand that filetype, so it won't display a preview of it.

Click on the "three dot" button in the upper right corner.

When you click on the three dot button, this menu should appear.

Choose "Open In"

Scroll to the right until you see the Books icon shown here. 

Click on that and the eBook should open in that app.