Although EPUB 3.0 has been a standard since October 2011, the adoption of the EPUB 3 standard by the major e-book retailers has been very slow, if non-existant.  Currently, iBooks and Vitalsource are the only two e-book platforms that are officially supporting EPUB 3 that I am aware of. Getting a complex book to work across iPads, Amazon, Kobo and Nook devices is undeniably a challenge. Read more »