Originally Posted by ATDrake
You don't need an special unzip script. ePubs are just ordinary zip files, arranged in a certain way. You can unzip them using your regular unzip tool ("unzip" in the Terminal, or just add a .zip extension to the filename and double-click in the Finder).
Hope this helps, and welcome to MobileRead!
The Finder doesn't always properly unzip scripts, and it's tedious renaming files or using the Terminal. I wrote the unzip script to make it faster and it always works. So to answer the question of where to download the unzip script. It's here (on page 2 of this thread):