Apple has released a free user guide eBook for iOS 6 in the iBookstore. iPhone User Guide For iOS 6 is a comprehensive guide to the new operating system and has tips on how to use the new iPhone.
Check it out: “Here’s everything you need to know about iPhone, in a handy eBook format. Get to know iPhone and discover all the amazing things it can do, and how to do them. It’s the definitive guide for getting the most from your new iPhone, straight from Apple. The iPhone User Guide is an essential part of any iPhone library.”
It’s got a handy description of how to organize your bookshelf in iBooks, like how to organize your eBooks and PDFs into collections. (Via TUAW).