How to load Books into iPad?

Latest Beta on both iMac, MacBook Pro, iPad, iPhone, and just to compete the cycle, iWatch. I want to add books to my iPad (used for in-house and real-world publications in epub). Once upon a time, a very simple process. Open iTunes (remember that program? Clunky but everythig worked), select Books (told you it was a while ago) and select the books to import. Now it's not so simple. If someone has figured out a way to load books into an iPad Pro, please tell me. I've tried File/Import, I've tried marking and drag and drop, I've used language that would have my mother washing my mouth out with soap. Nothing works.