Thanks Jellyby, I'll take a look at those links. I just want to know enough so that I can edit ePUb's already out there. Perhaps to edit the format a bit so that it seems nicer to me or add a ToC where one is missing. I've been using BD to convert/edit supported formats, but it's been kind of mind boggling with Epub's since there are so many different files associated with an Epub.
I've read that the CSS file contains the type of justification an Epub has. I was wondering if this can be changed if it's not a DRMed version and is it something that would be simple to do. For example, making an ePub fully justified if it was not.