I answered the question in email but also decided to publish it here in case others have the same question:
I think you want to go back to Google Books to find older books.
The two services are very different from each other, designed for entirely different purposes.
Google Play at https://play.google.com/store is the service to obtain digital books (mostly modern books that you have to pay for), music, games, and applications to an Android handheld computer. The entire purpose of Google Play is to make money for Google by charging the customers, although some of the apps are free. I suspect there are very few genealogy books in Google Play.
Google Books at http://books.google.com/ is a service for all computers (Windows, Macintosh, Linux, iPad, Google, and probably others) that scans old books in libraries and makes them available to read online or as downloads. Most of the older, out-of-copyright books in Google Books are available free of charge. Google Books contains hundreds, probably thousands, of genealogy and local history books.