The International Digital Publishing Forum (IDPF) created a new website a couple of weeks ago, that looks to be a good resource for information about the EPUB standard that they created and maintain. It's at EPUBZone.org. Even in the last couple of weeks they've updated it with news and a write-up of a recent seminar on using EPUB 3 as a platform to improve learning outcomes.
EPUB 3 is the latest version of EPUB, which is already a widely supported, publicly available standard for ebooks. The good thing about EPUB 3 from our perspective is that it includes both MathML and many more accessibility features than previous versions. That's because it's based on the new version of HTML that modern websites use. MathML support in ebooks makes mathematics accessible, searchable, and interoperable. With EPUB 3 it's easier to make all ebooks accessible, which helps authors and publishers meet government mandates on accessibility much more quickly and easily. There are many other features that eReaders are starting to support, which will make ebooks much more interactive in the future.
The EPUBzone website doesn't only have news articles, it also has articles on what EPUB 3 is, and how publishers can make best use of its features, including how best to include MathML and accessibility, as well as articles on ebook readers and publishing tools. We expect this to be a useful site to bookmark for reference.