Google has always been a fast-iterating company that welcomes feedback from customers on new features. It routinely launches betas and gives interested parties the chance to take a look at unfinished products. Just as it used to have an extensive collection of individual lab features in Gmail (called "advanced" today), the company is now giving Google Play Books users access to library features they can cherry-pick from.
At the moment, the Play Books team offers three functions for you to try out. The first one is "custom shelves," which allows you to organize books in whatever way you see fit. Genres, authors, length, fairytales, it's up to you. A button to create a shelf will appear in the sidebar, and once you've created and named your first custom collection, you can drag and drop books into it. The second feature adds additional filtering and sorting options to the interface. Lastly, you can activate a "ready to read" shelf that contains books you haven't finished. In my testing, everything seemed fairly stable and instantly available without a site refresh, albeit the design could use some polish (well, the Play Store web interface needs a fresh coat, generally).
The ability to let users choose which features they want to beta test is a welcome switch away from Google's usual A/B tests that come and go randomly. To try the Play Books beta options for yourself, head to play.google.com/books, click the settings icon, and then choose "Beta features." Unfortunately, there is no word on if or when these will be available in the Android app.
Check out the source link below if you're interested in the Play Books team's reasoning and modus operandi.