Just wondering, why do you say 'needs to use xcode 4'? I'd just focus on understanding the code, and game engine, etc... You also need some kinda game plan, figure out if you want 2d or 3d, turn based, MMOG, FPS, etc...
It really doesn't matter if the book covers xcode 4 or not, in fact it's a good challenge to learn the difference yourself.
One I just finished was using xcode 3, I had to figure out the difference as I use xcode 4. It added some challenge and makes to harder to become a 'cut and paste' programmer.
Then start looking at the game engines as Jnoxx pointed out, unity, cocos2d...
I'd actually pass on the books and look at the online blogs, videos, etc... Once you get a solid game plan, then you'll know what book to invest in.