The only right way to override fonts in my opinion is:
Code:
@font-face
{
font-family: sans-serif;
src:url(res://....);
}
@font-face
{
font-family: serif;
src:url(res://...);
}
@font-face
{
font-family: monospace;
src:url(res://...);
}
As this way you don't have to mess with CSS selectors.
Custom CSS works in all books, but some might have style that overrides yours, which is a generic CSS "issue". Check this:
Understanding the selectors priority