I started out developing for the Mac with "The Objective-C Programming Language" but found it clumsy and kind of dense. In my opinion "Cocoa Programming for Mac OS X" by Aaron Hillegass (http://www.amazon.com/Cocoa-Programming-Mac-OS-3rd/dp/032150...) is much better in the way it introduces concepts, and flows from chapter to chapter. Well worth the investment if you're serious about developing for the Mac.