I sometimes get email asking me about how I learned to be a Mac developer. Here’s a list of books that have been most important to me.
Learn C on the Macintosh by Dave Mark taught me how to program in C. Knowing C, even in this age of Java and Objective-C, is important. It’s the basis for everything else.
The C Programming Language by Kernighan and Ritchie is the essential reference. Years after initially learning C I still refer to it.
Writing Solid Code by Steve Maguire is about the philosophy and practices of development. It teaches, and even inspires, one to be rigorous and thorough.
Ultimate Mac Programming by Dave Mark appears to be out of print. This book taught me the Apple event manager. If you’re interested in Apple events, and can find this book, buy it.
Cocoa Programming for Mac OS X by Aaron Hillegass is an excellent introduction to Cocoa. I went from not really getting Cocoa to building my own apps before I was even half-way through the book.