From the IDPF:
As part of the ongoing EPUB 3 Implementation Project the Association for American Publishers (AAP) has made available a white paper that documents several outcomes of the cross-industry initiative, including the top 10 features deemed most critical for immediate implementation by participating publishers and reading system developers, as well as the top 13 tips for content publishers to create accessible EPUB 3 publications. For more information and to download the white paper, visit: http://publishers.org/press/117/ .