can recommend this
i've not done any Objective-C before, and though this book recommends that you should be a bit familiar with the language, i decided to dive right in and pick it up as i went along. and so far, it's going well. the book provides a nice learning curve and is quick to point out the differences between OS X coding and iPhone coding alongside the similarities. The writing style is very relaxed and easy to read - it reads more like being in a lecture than reading the textbook, if that makes sense?