The C Programming Language
Amazon
And I used Learning Cocoa to learn both Cocoa and Objective C.
Amazon
After that... you've got to learn Cocoa Touch and Objective C 2.0 but those are just extensions of Cocoa and Objective C 1.0... easy to just pick up on as you go along.
The above two books are the only ones I read and I think I'm doing pretty good... just asking a question or two (everyday) here when I come across something that's unique to Cocoa Touch or 2.0.
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