I used a similar workflow. The CSS is for the EPUB and maps to the html elements supported. But if you get too fancy cross device support could get hairy. See:

I used a similar workflow. The CSS is for the EPUB and maps to the html elements supported. But if you get too fancy cross device support could get hairy. See: https://github.com/FriendsOfEpub/Blitz https://github.com/FriendsOfEpub/Blitz