I'll be honest: if this is your first foray into software development, I worry that you might be jumping in a little too close to the deep end of the pool. But if you are dead set on getting to Objective-C as quickly as possible, then I'd at least suggest that you start by just learning C first, as everything you learn there will be directly applicable to Objective-C. Perhaps someone else can recommend a good book on C for a beginner. (I learned C from the pre-ANSI K&R ... i.e., "The C Programming Language" by Brian Kernighan and Dennis Ritchie, 1st ed. ... but it wasn't my first language, and that book wouldn't be a good text to use as an introduction to programming.)
After you've learned C, Apple has a downloadable PDF on Objective-C (for C programmers) that might be helpful for you in making the transition. You'd need an Apple Developer account to get that PDF. After you understand that and some of the basic tenants of object-oriented development, you could try to get started on learning the Cocoa framework with one of the books mentioned earlier in this thread.