Re: IOS development books?
If you're just looking for code references, I would buy whatever books best match your learning style.
I tend to think the hard part of developing for iOS is designing for mobile devices. To help with that, I recommend taking one of Sarah Parmenter's workshops
"It is logically impossible for people to know God exists without any proven evidence. It is, however logically plausible to believe something does not exist if there is no evidence of it."