Using the same value as the id attribute for the XHTML cover, add an initial itemref to the spine element that refers to the cover page but is not linear. This tells reading systems (like ADE) what position the XHTML cover should have in the document (must be first to trigger cover behavior), but asks that it not be displayed to the reader as part of the “linear reading order of the publication.”

By setting linear=”no” you run the risk that the reader won’t see the cover at all on some reading systems. It’s safe to leave this as linear=”yes” for ADE on the desktop and devices without it showing the cover twice.