[Daniele Comi]

Which is the best medium level android programming book?

[sekip]

Hey if you want to program games I recommend Learning Libgdx Game Development or Beginning Android 4 Games Development

[Zack Hine]

Android Programming: The Big Nerd Ranch Guide (Big Nerd Ranch Guides)

Search for that on Amazon. Very good book. Learned just about everything I know about Android Development from there.

[12er]

It depends. If you don't have any experience, I would recommend to work yourself through at least two books, a book about Java and a book about Android programming.
For learning Java I recommend the course notes of "Introduction to Programming in Java" from the Massachusetts Institute of Technology. I am not allowed to post links at this point, so simply do a google search for "MIT Introduction to Programming in Java", and get the course material from the first page of the search result. Implement small projects in Eclipse (regular project, not Android projects) for learning the major aspects of the Java programming language.
If you do have experience with Java, you are ready for learning about programming for Android: I found that "Resources every Android developer must know" by Sergey Povzner is a great resource for learning (google search for "Sergey Povzner Resources every Android developer must know" and open the first link). On this page you will find two recommended books (one with an online version, which can be downloaded as a pdf). Furthermore get yourself a full copy of Google's ADT onto your machine.

[funboy9]

I highly recommend "Professional android 4 application development"