- Google Books: Google has come up with an interesting alternative, by offering a cloud app that runs in the browser of any smartphone or mobile device (the user just types in the Web address http://m.google.com/books). Google provides access to more than 3 million books, and users can preview extensive portions of most of them for free. When you buy, you can store your purchases in the cloud as well. Google Books also offers a syncing function, so that you can switch devices if necessary, and an ingenious night-reading mode allows you to read white type on a black page [source: Google].
- Apple iBooks: This app, which runs only on iPhones and other Apple devices, allows you to purchase and read books in the ePub format from Apple's iTunes bookstore, which it stacks on a set of faux-wood shelves. It has similar features to Kindle app, with a few intriguing extras, such as a feature that reads certain books aloud to children [source: Apple].
- Kobo: This Canadian e-reader maker also offers a mobile app that runs on iPhone, Android and BlackBerry devices. The Kobo app offers many of the same features as its competitors, such as automatic syncing across devices, multiple fonts and day-or-night modes. In addition to a library of 2.5 million books, Kobo's big allure may be its social networking "Reading Life" feature. It allows users to discuss what they're reading and even to track and compare their reading habits -- such as what times of day they pick up books and how many pages they read -- with their peers [source: Kobo].
So which app is best for you? It depends upon what phone you have, what you're interested in reading, and what features appeal to you the most. The Kindle and Google apps run on the biggest range of devices, so if you have one of the less popular phone formats or think you may switch devices in the future, those may be good choices. If you're looking for the biggest libraries, the Nook, Kobo and Google apps are your best bet. When it comes to familiarity and ease of use, though, Kindle may be the best bet, since so many people also own Kindle e-reader devices.