Every so often I like to highlight a free eBook that helps you make eBooks. Today I would like to show you Publishing with iBooks Author, a guide that is free to download from O'Reilly. The book description has more detail:

This book is intended to get you up and writing in iBooks Author. You'll learn what to expect from this new tool and what its strengths and limitations are. You'll see how you can create beautifully designed pages and how you can bring those designs to life with interactive content in ways that, before now, were only possible in a web browser on the Internet. You'll also find out how to navigate the occasionally tricky terrain of Apple's ecosystem so that you can get your book published to the iBookstore.

You can find this eBook on the O'Reilly website. It's available for download as PDF, Epub, or Kindle.