Have you tried the following? Not sure if it'll work but it's worth a try. I recall playing with this the past weekend, but I don't have the relevant files in front of me now so I'll have to double-check when I get home.
<div class="dedication">To my wife</div>
<h1 class="chaptitle">Chapter 1</h1>
<p>First chapter goes here.</p>
Not at home right now, so I'll have to double-check, but iirc, I use the following for margins
I've never had luck centering text within div. Try using:
margin: 4em 0 4em 0;