I checked the official website and these are the supported methods of reading for MWS Reader:
- Text copied to the Clipboard (Shortcut: [CTRL] + [C])
- Documents (Microsoft Office, Acrobat Reader, OpenOffice.org, LibreOffice, etc.)
- Emails (Microsoft Outlook, Windows Live Mail, Mozilla Thunderbird, IncrediMail, etc.)
- Web pages (Edge, Internet Explorer, Firefox, Safari, Opera, Chrome, etc.)
- Text from eBooks, images, scanned documents and protected PDF files
As long as it supports a web page, and Google books are offered through a page, then it means you should be able to read the online e-books provided by Google.
Check the official website for additional information: http://www.mwsreader.com/en/