You can print PDFs, but not ePub books, as they are DRM locked and copyright does not permit making a hard copy.
see the iBook FAQ: http://support.apple.com/kb/HT5557
Also note that at this time, there is no way to view or open in iBook ePub book on your computer. The application, iBooks, is currently only available for iOS (although it is listed as a feature coming in OS X Mavericks later this year).