This is something I have been thinking about lately (and I have done in with two separate h# but wondering what best practice is), thank you pedrovic for asking and all you others for great responses!
If you do it like DNSB describes, how do you adjust the space between the two lines (besides putting multiple <br/>s)? (line-height could be used if the two lines are short enough to never use multiple lines on the device)
Also, what is the usuability to have the cover as a heading? I use headers as a way to get a toc, and for me, the cover shouldn't be there. What am I missing?