Originally Posted by EatingPie
You can also change User Agent in Safari, but you need to enable the Develop menu. To do so, go to Preferences->Advanced, and enable the option "Show Develop menu in menu bar" at the bottom.
Once you have the Develop Menu showing, the second item is a submenu allowing you to select various browsers, including IE 8.0.
I don't know why the Mac is limited to .pdb downloads. The newest version of the Nook Mac software supports ePUB. I was able to do the User Agent trick in Safari and open the ePUB in the Nook app.
Thank you for these instructions. I thought Safari was capable of this, but darned if I could figure out how to do it. So simple, too!