There's a reason that a large slice of the open-source movement has defected from running Linux on its laptops to running Mac OS X. The reason is the Unix core that underlies Mac OS X, and the development tools that run on that core. Cocoa makes it easy to create very slick Mac OS X interfaces for software (as well as to create applications in a hurry), and this new edition of Cocoa Programming for Mac OS X does an excellent job of teaching its readers how to put a Cocoa face on top of code (Objective-C code almost exclusively). If you know something about C and/or C++ programming and want to apply your skills to the Mac, this is precisely the book you want.