Android became the world's #1 and most popular mobile platform for smartphones, tablets, and smart TVs long ago. Whereupon, more and more people started out studying Android application development. At this point, a good book is very helpful. The Sams Teach Yourself series of books are all good, hence here AppNee recommends Sams Teach Yourself Android Application Development in 24 Hours to Android programming beginners (a bit outdated, but worth reading).

The Mono for Android launched by Novell is the industry's first solution using Microsoft Visual Studio to plan, build and develop Microsoft .NET based applications for Android platform. Professional Android Programming with Mono for Android and .NET / C# teaches you the Android application programming knowledge in a comprehensive and thorough way, including discussing how to combine the use of C# and Mono for Android to write applications run on all kinds of Android devices.