any apps similar to ibooks author?

Hello everyone, I own a macbook. I was looking under the "great free apps" in the app store and I noticed iBooks Author, I was super interested in it but then when I tried to download it, it said I didn't have the right software. Do you know of any other free apps like this one? Any help would be great because I really want this app. I don't have money to upgrade to OS X mountain lion either, so that is unfortunately not an option... thanks in advance!