But I strongly recommend you check out Programming iOS 4: http://oreilly.com/catalog/0636920010258
It's still in development and has just been updated to cover Xcode 4. I've been reading the previous edition and it's brilliant: great writing and the first half of the book is applicable to both iOS and desktop Cocoa development. As a relatively new Mac developer (1-2 years) this really consolidated my knowledge of Apple's frameworks and Objective-C.
Submit errata for the book when you find a mistake: For Learning iPhone Programming, it's http://www.oreillynet.com/cs/catalog/create/errata/?b=5073. For the Cookbook, it's http://www.oreillynet.com/cs/catalog/create/errata/?b=15595. We don't pay people for errata, but I'll make an offer to you and anyone else reading this: for every 10 new errata submissions of yours that we can confirm, I'll give you an O'Reilly ebook of your choice free.
Be a tech reviewer on an upcoming book: We do pay a modest honorarium for this. You'd be reading the book, looking for mistakes and other issues. Contact me for details.
To take me up on either offer, drop me an email at bjepson at oreilly. Act now, and I'll hook you up with an early access ebook for an upcoming book that I'm working on, Programming iOS 4: http://oreilly.com/catalog/0636920010258. I'd be interested in your opinion of that book.
Thanks,
Brian