Here's Episode 11 of Dirty Words Design, which discusses how to quickly edit and preview ePub files using iBooks for OS X.
Let's call this episode the first one of Season Two ... I'll be updating the blog to a new theme soon and working on more videos. Feels like I've got the bug again!
A few notes:
You can unhide your Library folder by first selection your Home folder in the Finder, then going to View -> Show View Options (Command-J), as seen in the screenshot below. If you are not in your Home folder, this option will not appear!
I use these scripts for unzipping and rezipping ePub files: http://www.mobileread.com/forums/showthread.php?t=55681—that post also contains the commands that you can use in Terminal if you prefer handling things that way!