While you're reading, the app offers quite a few options as far as visual styling goes. There are three themes to choose from: Day (black text on white background), Night (white text on black background), and Sepia. And of course, there are options to change zoom level, font size, typeface, text alignment, and line height. Additionally, you can choose to see either a clean, "Flowing text" version of the book, or the original scanned pages, which are certainly fun, though not as easy to read. Tablets can display pages side by side, while phones (even in horizontal mode) are stuck with a single page per screen.
When it comes to features, Google Play Books sits somewhere near the front of the e-reader pack, though that wasn't always the case. With the newest update to the app, users finally get integrated translation, maps, dictionary, and highlighting. To see the tools in action, simply tap and hold on a block of text from the page and wait for the options to appear. Depending on what your target text is, Google will show you a quick description or definition, links to Wikipedia, a translation (powered by Google Translate), or even a map of a location. For me, these tools have been indispensable, especially when I find myself reading works with a lot of non-English text. The highlighter is also useful, as it comes with four different color options and can be enabled by tapping a button on the top of the screen. Curiously, though, I haven't found a way to un-highlight text, which is infuriating. Also, for school-related reading, it would be a huge help to be able to name bookmarks.
By far, my biggest gripe about Google Play Books is that it doesn't import or sideload books. With so many sources of DRM-free e-books on the Web, not to mention my own personal collection of downloaded PDF e-books, it's a shame Google's e-reader app doesn't offer the feature. And I know there are swathes of users out there who feel the same way.