You'll need more that one book.
If you don't know how to program or develop any sort of software, all the iPhone books will likely be too steep a climb into an alien world. So first, go to your local library and get some good easy books on really introductory computer programming, any language, just pick ones you find easiest to read, and do some projects. Maybe even a book from the children's section to start off with.
Then, after the simple introductory programming projects seems easy, read the first few chapters of a book on C programming (C for dummys, et.al.). If you understand most of that, then try Hillegass's book on Cocoa Programming or Kochan's book on Obj-C. Then on to the books on the iPhone SDK.
No one book can sufficiently cover the above range.