I'm a newcomer to Objective-C and Cocoa but a reasonably experienced Java programmer. When I was starting out, reading Josh Bloch's Effective Java made me a 20% better Java programmer overnight. As its foreword says, most language books teach you syntax and vocabulary, but not much about idiomatic usage.
I hate knowing I'm writing "The vase of my uncle is on the credenza of my aunt" kind of stuff in a new language. What's the equivalent of Effective Java for Objective-C and Cocoa?