You can change views using the View menu.
You can create additional views of each type. For example you might create multiple table views each with a different set of columns.
You can create additional views by first selecting an existing view and then the View->Copy View menu item. You can now customize the new view.
You can also create, rename or delete views using Preferences.
Select the view you want to use and then the View->Save as Default View menu item.
For example if you wanted to use the thumbnail view as the default view, select it and save. Now when you restart the program Readerware will display the thumbnails of all your items.