It used to be fairly simple to add e-books (of the epub format) to your iPad or iPhone via your Mac, using iTunes file sharing. You’d simply drag and drop the book into iTunes, connect your iOS device, and sync the non-iBook file via the file sharing system in iTunes, just like any other file supported by apps on your iPad
With the advent of iBooks on the Mac with OS X Mavericks, there is no longer a way to sync epub books in this way. You might be stymied on attempting to get epubs from your Mac to your iPad, but thanks to an intrepid Cult of Mac reader, we all get to learn how to do just that.
First of all, open up your email client on the Mac. You can do this with any app or webmail program. Address an email to yourself, and attach the epub file you want to open on your iPad or iPhone. Send yourself the attachment, and then go grab your iOS device.
Now, open your preferred email program on your iPad or iPhone, and open up the email you just sent yourself. Tap the attachment icon to download it to your device, and you’ll see the icon turn into an iBooks one. Tap and hold on the file and an “Open in iBooks” will pop up. Tap that, and your iPad or iPhone will open iBooks and then open the epub file you just sent.
Thanks, John R!