There are not a lot of books on mobile development I have found to be that helpful so far. Recently I purchased the O'Reilly published Mobile Design Pattern Gallery book and want to recommend it. Its not a book deep in technical details, but rather a survey of UI patterns that work and don't work. It is rich on real life examples of UI patterns used in real applications with explanations of how each one exemplifies good and bad mobile design practices.
Personally I enjoy perusing some of the design pattern library resources online like the target='_blank'>Yahoo! Design Pattern Library and Infragistics Quince. While searching through these libraries I not only find some good ideas and inspiration, but they amaze me at how something like a design pattern can be organized. There are numerous site galleries available, but they never focus on how the UI is organized. Which is why I like these libraries. The Mobile Design Pattern Gallery book focuses on mobile only, which the typical library does not focus. In today's world of touch first mobile applications this is extremely important as most developers have not truly grasped concept key to great mobile experiences. This is why I want to recommend the Mobile Design Pattern Gallery by Theresa Neil.