<p>Objective-C is easy to learn, especially if you already know C. Objective-C is a superset of C that adds a thin layer of object-oriented features. Those features allow us to define classes with instance and class methods that look a lot like methods in Ruby, but these methods are <em>fast</em> because they are written in C. And unlike Java and C++, we don't need a shelf-full of books to use as a reference. </p>
<h2>Books</h2>
<p>Here are the three most important books for an Objective-C programmer to own.</p>
<ul>
<li><p>If you are comfortable with C, then just invest ten dollars in Andrew Duncan's <ahref="http://www.rubycocoa.com/book_review/objective-c-pocket-reference">Objective-C Pocket Reference (O'Reilly)</a>.
You can read it in an afternoon, and it contains all the Objective-C you'll need to know to use Nu.</p></li>
<li><p>If you want some help with C as well, then I recommend Stephen Kochan's <ahref="http://www.amazon.com/Programming-Objective-C-Stephen-Kochan/dp/0672325861/ref=pd_bbs_sr_1/002-5741156-2316003?ie=UTF8&s=books&qid=1191784252&sr=8-1">Programming in Objective-C</a>.
Experienced C programmers may find it a bit verbose, but it is comprehensive and accurate.</p></li>
<li><p>The definitive Objective-C compiler is <ahref="http://gcc.gnu.org">gcc</a>, and William von Hagen's <ahref="http://www.amazon.com/Definitive-Guide-GCC-Second/dp/1590595858/ref=sr_1_1/002-5741156-2316003?ie=UTF8&s=books&qid=1191784366&sr=1-1">Definitive Guide to GCC</a>
is an excellent resource for answering in-depth questions about compiling Objective-C programs.</p></li>
</ul>
<h2>Online</h2>
<ul>
<li><p>Apple's <ahref="http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/index.html#//apple_ref/doc/uid/TP30001163">Introduction to the Objective-C Programming Language</a>.</p></li>