In my opinions, a beautiful UI is extrem important for the success of app.
So now I'm searching a book about the User Interface design (at best) for Android, it should not be about the technical implementation, like how to create a menu or use different layouts. It should be more about the design concept.
The offical document: http://developer.android.com/design/index.html is great, but too short. I also found a book exact about this topic, but it's still not yet published until 2013.
So any suggestion about books in this topic would be thankful.