If you use iBooks on your iPad or iPhone, you can only read books in EPUB format. If you have books in text or PDF format you may want to convert them to EPUB so you can read them in iBooks. You can do this with Calibre, a free open-source e-book library application. It's easy! So easy, in fact, that this home-computing how-to from MacMost can present a full overview of the process in about five minutes. For more information, including detailed, step-by-step instructions, watch this Apple lover's guide.