Mac OS X navigate Digital Editions 4.5

I have a .ascm book uploaded to DE 4.5 and am trying to read it. There are 2 arrows in the menu bar of the app which are greyed out and I assume these move from page to page. Scrolling works but is amazingly slow and utterly unsatisfactory. Under the Reading Menu is Next and Previous which sort of work but one has to use the mouse to do so. Unless I'm missing something, this is an unbelievably bad application. How does one navigate through a book?