1) clean up the mess and remove the </p><br... mess
this will give a consistent base to work with.
2) add or increase the margin-top: value for the <p class=
(note: you may have more than 1 class to change. first paragraphs, indented paragraphs are not unusual. you might also have a class for Blockquotes.)
That should now give you a cleaner base to fine tune. I use .5em for my standard top margin on indented paragraph books. I raise it to .85 for block paragraphs
NB I am stingy with space that does not add to readability (with my tired eyes
) OTOH I don't go for the 'stark' look. either
