Apple released a set of six eBooks over the weekend just for iOS and Mac OS X developers. The developer guides are all available through Apple’s iBookstore, so you’ll need an iPhone, iPod touch or iPad and the iBooks app.
Apple’s developer guides in iBooks
The ebooks Apple is offering include iOS Human Interface Guidelines, iOS Technology Overview, iOS Application Programming Guide, Object Oriented Programming With Objective-C, Cocoa Fundamentals Guide, and The Objective-C Programming Language.
The books are available as free downloads for everyone at the iBookstore via the iBooks app. iBooks is available for the iPhone and iPod touch as well as the iPad as a free download at Apple’s iTunes-based App Store.