The book is called Cocoa and Objective-C: Up and Running. It’s a ground-level introduction to everything you need to write Cocoa apps. I don’t assume you know C or compilers, or anything other other how to use a Mac. It’s available now from O’Reilly Rough Cuts. More content will be added before it goes into production later this year.
Scott Stevenson writes a book about Cocoa and Objective-C and I’m sure this will be a good one. You can take a look into the current version at O’Reilly’s Rough Cuts site (the book’s website is located at CocoaBook.com). The best thing is that a lot of tutorials will find its way back to Cocoa Dev Central, an excellent place to start learning everything about Cocoa.