According to the changelogs, the app now uses the Readium SDK to add partial support for Epub3 features. Both fixed layout and reflowable ebooks are supported, as well as embedded sounds, animations, and videos, but little else in the way of Epub3 support is listed. The one other new feature mentioned is pop-up footnotes, something which iBooks has supported since 2012.
Other new features in this update include improvements to the highlights and bookmarks functions; text selection and highlights are now editable in PDF and EPUB 2 (in the iOS app), and that app also has an annotations panel. There is also a mention of improved annotations support for the Android app, but it's not clear what that means.
The app also boasts a night mode and custom reading themes. Readers will also have the option of opening Epub3 ebooks in either Epub3 or Epub2 compatibility modes, which should prove useful should they encounter an ebook which has features from both formats.
Please note: The new features have only been added to the paid versions of the Mantano app; the free version in Google Play hasn't been updated since February.