And sorry, but the page-flipping animation immediately puts me in a critical mood: it's not even subtle, it's a really over-the-top one. It blocks highlighting/selecting text, which negates the main value of reading electronic books: immediate access to dictionaries, encyclopedias, and reference sources.
I don't like the narrow, san-serif font. A good san-serif font can be quite clean and readable, but this one is too narrow IMO.
The drop cap words look terrible, typographically, misaligned and jarring. I don't understand why you're (inconsistently?) using drop cap words, initial drop caps, and paragraph headings without drop caps. The style is all over the place.
The animated illustrations are great! They add a ton of useful information to the text.