Stanza doesn't currently display any initial opening text; it is a bit like Preview.app or Notepad.exe in that regard. You can open books by selecting the "File"->"Open" menu item.

As Stanza moves along the beta process, we expect to include some initial help text in the screen to guide the user along commonly used tasks. If you have any specific questions on how to use Stanza to load books and transfer them to your iPhone/iPod (which is discussed at http://www.lexcycle.com/faq/how_to_get_books_onto_stanza_iphone), please don't hesitate to let us know.