To open epub3 GH file in BOOKs app (iPhone, IPad)

Procedure:

1. Download the file to your iPhone, iPad
2. After downloading – PRESS and HOLD epub3 icon until new window pops out – and choose SHARE
3. Move second row with apps at the end where are three dots  …MORE
4. Press …MORE
5. Under SUGGESTIONS choose COPY TO BOOKS
6. And now you can read it as a book