Effective Objective-C 2.0: 52 Specific Ways to Improve Your IOS and OS X Programs (Effective Software Development)
iOS 6 By Tutorials: Volume 1
iOS 6 By Tutorials: Volume 2
iOS Programming: The Big Nerd Ranch Guide (Big Nerd Ranch Guides)
Cocoa Programming for Mac OS X
Cocoa Design Patterns (Developer's Library)
Core Data: Apple's API for Persisting Data on Mac OS X: Apple's API for Persisting Data Under Mac OS X