As I understand, one could "transfer" Hype projects to XCode and then build an app from that.
And yes iBooks and iOS apps will only work on the iPads and iPhones.
If you want to expand your reach with interactive book media you would also want to pack your HTML files for Android and Windows Slate and Windows Phone.
Using Cordova will get you what you need for Android
Windows Phones and Slate you might want to start here.