Exploring Mac App Development Strategies (Feedback Request)

I wrote and released a book called "Exploring Mac App Development Strategies" which helps developers design reusable code and untangle Core Data from their app, for example.

I have another writing projects in the queue, so first, I'd like to get your honest feedback on the topic. There's not a lot of literature on maintaining Cocoa code. I'd like to change that.

What do you think of the book?