[Turtle91]

You can either insert a <br /> where you want to break up long sentences, or you can use an &nbsp; between words you really don't want to split.
eg:
<h1>Royal Wedding<br />or<br />Sinister Plot?</h1>
- or -
<h1>Royal&nbsp;Wedding or Sinister&nbsp;Plot?</h1>

That will let the device/app know where it can split between those words.

Splitting the words themselves is a function of the device's hyphenation rules. You can add some css rules to your <h1> telling it not to hyphenate, but that doesn't mean that particular app/reader will obey the css rules...

h1 {
-webkit-hyphens: none;
-moz-hyphens: none;
-ms-hyphens: none;
hyphens: none
}

A combination of the two techniques should work for almost all circumstances.
Cheers!