how to open epub file in iBook from app

Question

How to download epub file and open it in iBook in my swift app. I tried to handle it like this:

var urlAt = NSURL(string: epubFileUrl);
    if (UIApplication.sharedApplication().canOpenURL(urlAt!)){
        UIApplication.sharedApplication().openURL(urlAt!);
    }

The app opened safari, downloaded my file and suggested me "how to open this file"

My question - can I download my epub file in my app, and open (or suggest to open) it in iBooks app.