Instruct: Classify a given review into positive or negative sentiment.
Query: The best book out there on a confusing topic

Cocoa can seem like a brave new world to those accustomed to pure programming, since Cocoa is a combination of programming in Objective-C and stringing together and customizing prefabricated visual components. So it was comforting to read this in chapter one: "Before going any further, assure yourself that you are up to the challenge and that some things are just hard." You should already know Objective-C before you read this book. If you don't, "Programming In Objective-C" by Kochan is a good book on the subject. Just be prepared for the difficulty level going through the book to be more like hills and valleys than one long ascension. This is not to say that the book is not a good one, it's just that since Cocoa is actually an umbrella for a number of technologies that it is really hard to start from the beginning since there really isn't one. There are plenty of examples though, and the author makes the subject as clear as is humanly possible.