Programming in Objective-C - Kochan (http://www.amazon.com/Programming-Objective-C-4th-Developers...) I am currently halfway through this book, it is primarily focused on the actual Objective-C language, and almost nothing on actual iOS/Cocoa Development (some small bits in the later chapters). I was recommended this to learn the underlying language before jumping in, very enjoyable so far, the exercises are great.
I have heard good things about both Nerd Ranch books (http://www.amazon.com/iOS-Programming-Ranch-Guide-Guides/dp/...) and will likely use that for introduction to Cocoa and iOS SDK.
Originally I planned on using "Beginning iOS 5 Development" from Apress as the iOS SDK learning book (http://www.amazon.com/Beginning-iOS-Development-Exploring-SD...), but it seems that the reviews are quite low compared to previous versions.
Finally, if you enjoy learning through video, the Stanford course is very highly recommended, through iTunes (http://itunes.apple.com/us/itunes-u/ipad-iphone-application-...). I found them very useful to start with, but I felt I wasn't learning much syntax through the videos, the talking portions are very in depth, but the coding portions are very quick (and went over my head due to not knowing Objective-C!). I will likely return to these when I have a working understanding of Objective-C.
(Most of these tips from my understanding of: http://stackoverflow.com/questions/3403049/best-book-resourc... and http://stackoverflow.com/questions/1939/how-to-articles-for-...)
If you want an intensive study of Objective C itself, look at the Kochan book. It's the bible.
http://www.stanford.edu/class/cs193p/cgi-bin/drupal/
http://www.amazon.com/Programming-Objective-C-Edition-Develo...
http://www.amazon.com/iOS-Programming-Ranch-Guide-Guides/dp/...
In relation to the criteria you raised the book is a good fit.
- I understand most of the basic concepts, but cannot implement them via code
I think this is particularly true with iOS programming. The book is more written in a tutorial / HowTo style (i.e. the book gives a step by step walkthrough to create an example program). Most importantly it specifies how to use the IDE to do GUI building.
- I am a person that does really well when I have a set path
Me too. Each chapter is an exercise designed to teach you some part of the iOS library. There about 30 chapters in the book and each chapter can be completed in about 2 hours.