Kochan's book is great for the language itself. But, that doesn't help you with the frameworks. For that, I'm a huge fan of Hillegass' Cocoa Programming (and its how I first picked up Cocoa), but, I'd only recommend it if you're more interested in the Mac than the iPhone. AppKit and UIKit are different beasts to learn.
Jeff LaMarche and David Mark's Beginning iPhone Development, Bill Dudney and Chris Adamson's iPhone SDK Development or Erica Sadun's iPhone Developers Cookbook are all very good books to look into (although, I vaguely remember hearing something like that Erica is working on another edition that covers iPad additions. May be worth holding off on this particular book for a bit..).
The problem is, the really fun stuff (Game Center, multitasking, and iAd to name some; there's many more fun things that are.) is still under NDA. Or maybe there's not many printed books written on the topic, period (Blocks/GCD, AddressBook, using Instruments to debug/optimize your app, etc). So you want to figure out how to read the docs and guides from Apple as quickly as you can. Which, luckily, isn't too bad to do — the docs tend to be very well written.
