On the Scholastic Storia Faq
, they say:
Storia eBooks are designed with unique learning features and enrichments that make them readable only while using the Storia eReading app.
So it'll be a proprietary format (or an extension of an existing one) that won't convert, DRM or not. There is, however an Android app which may work with the Fire. (I can't try it as both the Fire and the Storia app are only available in the US)