Begining iPhone Development, Exploring the SDK - Great book which covers many iPhone graphical interfaces. The book focus on DSK development. Please note that this book doesn't cover Objective-C

iPhone in action - Good book which covers both Web development and iPhone SDK development. The books covers also little of Objective-C.

Learn Objective-C on the Mac - iPhone & Mac programming have much in common. Both use Objective-C object oriented programming. This book will assist you to learn the Objective-C programming language.