Here's how you can download the iBooks Author app free for your Mac.
1. Go to the iBooks Author app preview page.
2. Click the View in Mac App Store button.
3. Click the Free button to download the app.
Here's a description and screenshot of iBooks Author for Mac:
"Now anyone can create stunning iBooks textbooks, cookbooks, history books, picture books, and more for iPad. All you need is an idea and a Mac.
Start with one of the Apple-designed templates that feature a wide variety of page layouts.
Add your own text and images with drag-and-drop ease. Use Multi-Touch widgets to include interactive photo galleries, movies, Keynote presentations, 3D objects, and more. Preview your book on your iPad at any time.
Then submit your finished work to the iBookstore in a few simple steps. And before you know it, you’re a published author."