@charleski Thanks for that Info! I am glad to know the differences with ID4 and ID5. Our small publishing house JUST paid for upgrading to ID4, and we are not willing to go to ID5 until we see some real benefits. As it is, the ID4 output can be easily converted to something sigil-ready so we are content to stand pat.
@alda: The epub format may seem intimidating at first, but actually it is quite understandable. Don't give up too soon. As tools, look at sigil and calibre, especially the discussions in these forums (and of course this epub forum itself), and you'll soon get a grasp on the issues.
One of the strange and wonderful things that I've observed is that "small" publishers are more than willing to share what they've learned in order to help other small publishers. This is in contrast to the "large" brick-and-mortar publishers. So just ask, if you have further questions.