I meant to reply to this earlier, but... Don't get the Learning Cocoa with Objective-C book. It was written 7 years ago and is basically a rehash of the (old) documentation.
I think that Scott's book is probably a good choice for getting started (more so than Hillegass' which is excellent but requires knowledge of OO programming and C; once you know those, though, you need to read it). Of course all the caveats of buying a rough cut apply, but I think you should be okay.
That said, I tried to learn Cocoa and Objective-C from the first book you mentioned and Hillegass' book (I even got pretty far) for years, but I never really grokked it until this summer when I had to write an iPhone app. To get up to speed, I went through Apress' well-paced, accessible series: Learn C on the Mac; Learn Objective-C on the Mac; and Beginning iPhone Development. If you want to start from the beginning, I highly recommend the series. If you sit down with each book and just completely go through all of the projects, you can get through all three of them in a week or two (with 4-6 hours of studying a day, with a few free days).
It's pretty difficult to get lost in that series, and they're in depth enough to give you a good conceptual understanding of each of the languages and frameworks. Once I went through those, it was much easier to understand Hillegass' book, the Cocoa Design Patterns book that's coming out, and pretty much any information on Cocoa available on the web. I highly recommend them.