Haha, I also set learning iOS as one of my 2012 resolutions AND I also bought TBNR after reading good reviews in Amazon. The 2nd edition covers Xcode 4 and iOS 4 (a bit outdated, but my target market is iOS 4+ anyway).
The shameful thing is, I haven't read the book yet, and instead go with Titanium since I'm more familiar with JavaScript (not really, but better than zero experience with Objective-C). It's been a couple of days, and things are doing good (but debugging sucks).
I eventually will learn iOS/Objective-C, but since I come from Java, and I don't like Xcode (I've played around a bit) I will most likely use AppCode from JetBrains.