Translation and other new features have come to Play Books in the latest version of the app, which is currently sitting at version number 3.15.5. Once you've selected a block of text on screen and after you're done highlighting everything you want, you'll end up with the action menu that offers you options on what to do with that highlighted text. One of these options will now be the translation button and tapping this will let you select the language you want to translate to, while the language you're translating from should already be set as whatever default language the book text is in.
In addition to the new translation feature that Google added in, Play Books also now supports faster highlighting with stylus pens, so if you need to mark something off on a certain page and you have a device like the Galaxy Note 8, you can use the S Pen to highlight blocks of text rather quickly and easily compared to before. This is because text selection with the stylus is now automatic as soon as you touch the stylus to the screen instead of having to long press on the portion of text you want to highlight first. What's more is that the action menu pops right up after you lift the stylus back off the page, so the act of highlighting content and doing something with it is a little easier if you're using the app with a stylus on-hand, and this is especially true since the highlighting begins as soon as you start dragging the stylus across the screen.
Notes are another new feature which are now supported by stylus in Play Books, and once again this is an option you'll find accessible from the action menu after you've highlighted the text you want to make a note of. Once the action menu pops up, simply tap the new note button that should reside to the left-most part of the menu, and you'll be able to write up whatever you need about that selected portion of text, and notes still store to the notes screen automatically so you won't have to do anything more than just write down what you want. If you haven't officially gotten the update for the app yet and you want access to these new features, you can grab the APK from the button below.