Google is starting to focus Android on mobile devices, as seen in this version 4. Some readers who are mobile developers will undoubtedly think this is far overdue. But at least it is here. Some chapters of this book explain fairly mundane new aspects, like the action bar or the GridLayout. Or the last chapter on different screen sizes and how to code to support these using the same code base. The GridLayout reminds me of the java classes for grids that were often awkward to code for desktop applications. At least the book's examples seem simpler. For these GUI changes, you should be able to follow the code snippets readily. Nothing intricate here. What is more interesting is the social and calendar APIs. These are qualitatively quite dissimilar from the other chapters. They show that Google has taken a close look at how to combine the mobile device with human interactions in a fruitful manner. This especially includes the use of photos of your friends and colleagues. Essentially, a data class is devised that has a name, email, phone number and photo. A very natural grouping of associated information. With this, the device can build up and let you access wirelessly your social network. In a somewhat related aspect, the Calendar APIs let you plug into pre-existing calendars, stored perhaps on your Google accounts, and access them easily on the cellphone. The book's discussion of this is rather rudimentary however, and could bear with some expansion in a future edition.